From 2341fc32a86d7855d2450d1a6aa211bf3f5d393d Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Tue, 9 Dec 2025 22:02:11 +0900
Subject: [PATCH 01/45] =?UTF-8?q?docs:=20=EC=88=98=EA=B0=95=EC=8B=A0?=
 =?UTF-8?q?=EC=B2=AD=20=EB=8F=84=EB=A9=94=EC=9D=B8=20=EB=AA=A8=EB=8D=B8=20?=
 =?UTF-8?q?=EB=AC=B8=EC=84=9C=20=EC=B6=94=EA=B0=80=20=EB=B0=8F=20=EB=A7=81?=
 =?UTF-8?q?=ED=81=AC=20=EC=88=98=EC=A0=95?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

README.md
- 2단계 문서 링크를 `02-lms-domain-model.md`로 올바르게 연결하도록 수정

docs/02-lms-domain-model.md
- 수강신청 도메인 모델 요구사항 문서 신규 추가
- LMS 개요 및 기능 요구사항 구조화
- 프로그래밍 요구사항 및 TDD 원칙 명시
---
 README.md                   |  2 +-
 docs/02-lms-domain-model.md | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+), 1 deletion(-)
 create mode 100644 docs/02-lms-domain-model.md

diff --git a/README.md b/README.md
index c3596da16..53b7c3ff0 100644
--- a/README.md
+++ b/README.md
@@ -3,7 +3,7 @@
 본 저장소는 TDD 학습을 위한 단계별 과제를 포함합니다.
 ## 단계별 문서
 - **[1단계 - 레거시 코드 리팩터링](./docs/01-legacy-code-refactoring.md)**
-- **[2단계 - 수강신청(도메인 모델)]()**
+- **[2단계 - 수강신청(도메인 모델)](./docs/02-lms-domain-model.md)**
 - **[3단계 - 수강신청(DB 신청)]()**
 - **[4단계 - 수강신청(요구사항 변경)]()**
 ## 진행 방법
diff --git a/docs/02-lms-domain-model.md b/docs/02-lms-domain-model.md
new file mode 100644
index 000000000..234e52c03
--- /dev/null
+++ b/docs/02-lms-domain-model.md
@@ -0,0 +1,33 @@
+# 2단계 - 수강신청(도메인 모델)
+***
+## 코드 리뷰
+> PR 링크:
+> 
+## 나의 학습 목표
+- TDD 사이클로 구현
+- 객체지향 생활 체조 원칙 준수
+- 테스트 작성하기 쉬운 구조로 설계
+- 자기 점검 체크리스트 준수
+## 학습 관리 시스템(LMS)
+- 넥스트스텝은 재직자를 대상으로 소프트웨어 교육을 진행하는 교육 기관이다.
+- 2018년 교육 사업을 시작했다.
+- 교육 사업을 시작하며 자체적으로 학습 관리 시스템을 개발해 수강생을 모집하고, 컨텐츠를 관리하고 있다.
+## 수강 신청 기능 요구사항
+- 과정(Course)은 기수 단위로 운영하며, 여러 개의 강의(Session)를 가질 수 있다.
+- 강의는 시작일과 종료일을 가진다.
+- 강의는 강의 커버 이미지 정보를 가진다.
+  - 이미지 크기는 1MB 이하여야 한다.
+  - 이미지 타입은 gif, jpg(jpeg 포함),, png, svg만 허용한다.
+  - 이미지의 width는 300픽셀, height는 200픽셀 이상이어야 하며, width와 height의 비율은 3:2여야 한다.
+- 강의는 무료 강의와 유료 강의로 나뉜다.
+  - 무료 강의는 최대 수강 인원 제한이 없다.
+  - 유료 강의는 강의 최대 수강 인원을 초과할 수 없다.
+  - 유료 강의는 수강생이 결제한 금액과 수강료가 일치할 때 수강 신청이 가능하다.
+- 강의 상태는 준비중, 모집중, 종료 3가지 상태를 가진다.
+- 강의 수강신청은 강의 상태가 모집중일 때만 가능하다.
+- 유료 강의의 경우 결제는 이미 완료한 것으로 가정하고 이후 과정을 구현한다.
+  - 결제를 완료한 결제 정보는 payments 모듈을 통해 관리되며, 결제 정보는 Payment 객체에 담겨 반한된다.
+## 프로그래밍 요구사항
+- DB 테이블 설꼐 없이 도메인 모델부터 구현한다.
+- 도메인 모델은 TDD로 구현한다.
+  - 단, Service 클래스는 단위 테스트가 없어도 된다.
\ No newline at end of file

From 18aecc7330ca04c6533733357a39fc57e35a687c Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Tue, 9 Dec 2025 22:27:08 +0900
Subject: [PATCH 02/45] =?UTF-8?q?feat:=20Course=EC=97=90=20generation=20?=
 =?UTF-8?q?=ED=95=84=EB=93=9C=20=EC=B6=94=EA=B0=80=20=EB=B0=8F=20=EC=A0=80?=
 =?UTF-8?q?=EC=9E=A5/=EC=A1=B0=ED=9A=8C=20=EA=B8=B0=EB=8A=A5=20=ED=99=95?=
 =?UTF-8?q?=EC=9E=A5?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Course.java
- generation 필드 추가 및 Getter 구현
- 생성자 오버로드 수정 및 generation 반영
- 기존 필드 포함한 신규 전체 생성자 정의

JdbcCourseRepository.java
- insert 쿼리에 generation 컬럼 추가
- findById 조회 시 generation 매핑 추가 및 파라미터 인덱스 조정

schema.sql
- course 테이블에 generation 컬럼 추가 (NOT NULL)

CourseTest.java
- generation 포함 생성자 정상 생성 테스트 추가

CourseRepositoryTest.java
- generation 포함한 Course 저장/조회 검증 추가
- createdAt 값 비교 테스트 추가
---
 .../java/nextstep/courses/domain/Course.java   | 18 +++++++++++++++---
 .../infrastructure/JdbcCourseRepository.java   | 14 ++++++++------
 src/main/resources/schema.sql                  |  1 +
 .../nextstep/courses/domain/CourseTest.java    | 18 ++++++++++++++++++
 .../infrastructure/CourseRepositoryTest.java   |  7 ++++++-
 5 files changed, 48 insertions(+), 10 deletions(-)
 create mode 100644 src/test/java/nextstep/courses/domain/CourseTest.java

diff --git a/src/main/java/nextstep/courses/domain/Course.java b/src/main/java/nextstep/courses/domain/Course.java
index 176e0617b..97e5b383c 100644
--- a/src/main/java/nextstep/courses/domain/Course.java
+++ b/src/main/java/nextstep/courses/domain/Course.java
@@ -7,6 +7,8 @@ public class Course {
 
     private String title;
 
+    private int generation;
+
     private Long creatorId;
 
     private LocalDateTime createdAt;
@@ -15,13 +17,19 @@ public class Course {
 
     public Course() {}
 
-    public Course(String title, Long creatorId) {
-        this(0L, title, creatorId, LocalDateTime.now(), null);
+    public Course(String title, int generation, Long creatorId, LocalDateTime now) {
+        this(0L, title, generation, creatorId, now, null);
+    }
+
+    public Course(String title, int generation, Long creatorId) {
+        this(0L, title, generation, creatorId, LocalDateTime.now(), null);
     }
 
-    public Course(Long id, String title, Long creatorId, LocalDateTime createdAt, LocalDateTime updatedAt) {
+    public Course(
+            Long id, String title, int generation, Long creatorId, LocalDateTime createdAt, LocalDateTime updatedAt) {
         this.id = id;
         this.title = title;
+        this.generation = generation;
         this.creatorId = creatorId;
         this.createdAt = createdAt;
         this.updatedAt = updatedAt;
@@ -35,6 +43,10 @@ public Long getCreatorId() {
         return creatorId;
     }
 
+    public int getGeneration() {
+        return generation;
+    }
+
     public LocalDateTime getCreatedAt() {
         return createdAt;
     }
diff --git a/src/main/java/nextstep/courses/infrastructure/JdbcCourseRepository.java b/src/main/java/nextstep/courses/infrastructure/JdbcCourseRepository.java
index 3075de280..3f21435f7 100644
--- a/src/main/java/nextstep/courses/infrastructure/JdbcCourseRepository.java
+++ b/src/main/java/nextstep/courses/infrastructure/JdbcCourseRepository.java
@@ -18,19 +18,21 @@ public JdbcCourseRepository(JdbcOperations jdbcTemplate) {
 
     @Override
     public int save(Course course) {
-        String sql = "insert into course (title, creator_id, created_at) values(?, ?, ?)";
-        return jdbcTemplate.update(sql, course.getTitle(), course.getCreatorId(), course.getCreatedAt());
+        String sql = "insert into course (title, generation, creator_id, created_at) values(?, ?, ?, ?)";
+        return jdbcTemplate.update(
+                sql, course.getTitle(), course.getGeneration(), course.getCreatorId(), course.getCreatedAt());
     }
 
     @Override
     public Course findById(Long id) {
-        String sql = "select id, title, creator_id, created_at, updated_at from course where id = ?";
+        String sql = "select id, title, generation, creator_id, created_at, updated_at from course where id = ?";
         RowMapper<Course> rowMapper = (rs, rowNum) -> new Course(
                 rs.getLong(1),
                 rs.getString(2),
-                rs.getLong(3),
-                toLocalDateTime(rs.getTimestamp(4)),
-                toLocalDateTime(rs.getTimestamp(5)));
+                rs.getInt(3),
+                rs.getLong(4),
+                toLocalDateTime(rs.getTimestamp(5)),
+                toLocalDateTime(rs.getTimestamp(6)));
         return jdbcTemplate.queryForObject(sql, rowMapper, id);
     }
 
diff --git a/src/main/resources/schema.sql b/src/main/resources/schema.sql
index 8d5a988c8..746fcb244 100644
--- a/src/main/resources/schema.sql
+++ b/src/main/resources/schema.sql
@@ -1,6 +1,7 @@
 create table course (
     id bigint generated by default as identity,
     title varchar(255) not null,
+    generation INT NOT NULL,
     creator_id bigint not null,
     created_at timestamp not null,
     updated_at timestamp,
diff --git a/src/test/java/nextstep/courses/domain/CourseTest.java b/src/test/java/nextstep/courses/domain/CourseTest.java
new file mode 100644
index 000000000..58e5bd30d
--- /dev/null
+++ b/src/test/java/nextstep/courses/domain/CourseTest.java
@@ -0,0 +1,18 @@
+package nextstep.courses.domain;
+
+import static org.assertj.core.api.Assertions.*;
+
+import java.time.LocalDateTime;
+import org.junit.jupiter.api.DisplayNameGeneration;
+import org.junit.jupiter.api.DisplayNameGenerator;
+import org.junit.jupiter.api.Test;
+
+@DisplayNameGeneration(DisplayNameGenerator.ReplaceUnderscores.class)
+class CourseTest {
+
+    @Test
+    void 생성자_정상입력_생성성공() {
+        LocalDateTime fixedNow = LocalDateTime.now();
+        assertThatCode(() -> new Course("과정명", 1, 1L, fixedNow)).doesNotThrowAnyException();
+    }
+}
diff --git a/src/test/java/nextstep/courses/infrastructure/CourseRepositoryTest.java b/src/test/java/nextstep/courses/infrastructure/CourseRepositoryTest.java
index 1289b7fe5..c79525793 100644
--- a/src/test/java/nextstep/courses/infrastructure/CourseRepositoryTest.java
+++ b/src/test/java/nextstep/courses/infrastructure/CourseRepositoryTest.java
@@ -2,6 +2,7 @@
 
 import static org.assertj.core.api.Assertions.assertThat;
 
+import java.time.LocalDateTime;
 import nextstep.courses.domain.Course;
 import nextstep.courses.domain.CourseRepository;
 import org.junit.jupiter.api.BeforeEach;
@@ -28,11 +29,15 @@ void setUp() {
 
     @Test
     void crud() {
-        Course course = new Course("TDD, 클린 코드 with Java", 1L);
+        LocalDateTime fixednow = LocalDateTime.now();
+        Course course = new Course("TDD, 클린 코드 with Java", 1, 1L, fixednow);
         int count = courseRepository.save(course);
         assertThat(count).isEqualTo(1);
         Course savedCourse = courseRepository.findById(1L);
         assertThat(course.getTitle()).isEqualTo(savedCourse.getTitle());
+        assertThat(course.getGeneration()).isEqualTo(savedCourse.getGeneration());
+        assertThat(course.getCreatorId()).isEqualTo(savedCourse.getCreatorId());
+        assertThat(course.getCreatedAt()).isEqualTo(savedCourse.getCreatedAt());
         LOGGER.debug("Course: {}", savedCourse);
     }
 }

From ed41d5bc85ea0dbba1b85880ca60d2fc4e4dcdc5 Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 06:34:03 +0900
Subject: [PATCH 03/45] =?UTF-8?q?feat:=20=EC=9D=B4=EB=AF=B8=EC=A7=80=20?=
 =?UTF-8?q?=ED=83=80=EC=9E=85=20enum=20=EC=B6=94=EA=B0=80=20=EB=B0=8F=20?=
 =?UTF-8?q?=EB=B3=80=ED=99=98=20=EB=A1=9C=EC=A7=81=20=EA=B5=AC=ED=98=84?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

ImageType.java
- GIF, JPG, PNG, SVG enum 정의
- jpeg 입력 시 JPG로 매핑하는 from() 메서드 구현
- 미지원 타입은 기존 valueOf에서 예외 발생

ImageTypeTest.java
- jpeg 입력 시 JPG 반환 테스트 추가
- 미지원 타입 입력 시 예외 발생 테스트 추가
---
 .../nextstep/courses/domain/ImageType.java    | 15 +++++++++++++
 .../courses/domain/ImageTypeTest.java         | 21 +++++++++++++++++++
 2 files changed, 36 insertions(+)
 create mode 100644 src/main/java/nextstep/courses/domain/ImageType.java
 create mode 100644 src/test/java/nextstep/courses/domain/ImageTypeTest.java

diff --git a/src/main/java/nextstep/courses/domain/ImageType.java b/src/main/java/nextstep/courses/domain/ImageType.java
new file mode 100644
index 000000000..8fddcd68a
--- /dev/null
+++ b/src/main/java/nextstep/courses/domain/ImageType.java
@@ -0,0 +1,15 @@
+package nextstep.courses.domain;
+
+public enum ImageType {
+    GIF,
+    JPG,
+    PNG,
+    SVG;
+
+    public static ImageType from(String extension) {
+        if (extension.equals("jpeg")) {
+            return JPG;
+        }
+        return valueOf(extension);
+    }
+}
diff --git a/src/test/java/nextstep/courses/domain/ImageTypeTest.java b/src/test/java/nextstep/courses/domain/ImageTypeTest.java
new file mode 100644
index 000000000..1a23bdcfa
--- /dev/null
+++ b/src/test/java/nextstep/courses/domain/ImageTypeTest.java
@@ -0,0 +1,21 @@
+package nextstep.courses.domain;
+
+import static org.assertj.core.api.Assertions.*;
+
+import org.junit.jupiter.api.DisplayNameGeneration;
+import org.junit.jupiter.api.DisplayNameGenerator;
+import org.junit.jupiter.api.Test;
+
+@DisplayNameGeneration(DisplayNameGenerator.ReplaceUnderscores.class)
+class ImageTypeTest {
+
+    @Test
+    void from_JPEG입력_JPG반환() {
+        assertThat(ImageType.from("jpeg")).isEqualTo(ImageType.JPG);
+    }
+
+    @Test
+    void from_지원하지않는타입_예외발생() {
+        assertThatThrownBy(() -> ImageType.from("bmp")).isInstanceOf(IllegalArgumentException.class);
+    }
+}

From f7e3a1032fc45021f2e881f908fc32bd307f3f57 Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 06:36:27 +0900
Subject: [PATCH 04/45] =?UTF-8?q?refactor:=20ImageType=20=EB=8C=80?=
 =?UTF-8?q?=EC=86=8C=EB=AC=B8=EC=9E=90=20=EC=B2=98=EB=A6=AC=20=EA=B0=9C?=
 =?UTF-8?q?=EC=84=A0=20=EB=B0=8F=20=ED=8C=8C=EB=9D=BC=EB=AF=B8=ED=84=B0?=
 =?UTF-8?q?=ED=99=94=20=ED=85=8C=EC=8A=A4=ED=8A=B8=20=EC=B6=94=EA=B0=80?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

ImageType.java
- 확장자 입력값을 대문자로 변환 후 처리하도록 개선
- JPEG → JPG 매핑 조건을 대문자 기준으로 수정
- valueOf 호출 시 대문자 사용으로 케이스 민감도 문제 해결

ImageTypeTest.java
- PNG 입력값에 대해 파라미터화된 변환 성공 테스트 추가(png/PNG)
- 기존 JPEG → JPG 테스트 유지
---
 src/main/java/nextstep/courses/domain/ImageType.java     | 5 +++--
 src/test/java/nextstep/courses/domain/ImageTypeTest.java | 8 ++++++++
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/src/main/java/nextstep/courses/domain/ImageType.java b/src/main/java/nextstep/courses/domain/ImageType.java
index 8fddcd68a..9fb5d6d6c 100644
--- a/src/main/java/nextstep/courses/domain/ImageType.java
+++ b/src/main/java/nextstep/courses/domain/ImageType.java
@@ -7,9 +7,10 @@ public enum ImageType {
     SVG;
 
     public static ImageType from(String extension) {
-        if (extension.equals("jpeg")) {
+        String upper = extension.toUpperCase();
+        if (upper.equals("JPEG")) {
             return JPG;
         }
-        return valueOf(extension);
+        return valueOf(upper);
     }
 }
diff --git a/src/test/java/nextstep/courses/domain/ImageTypeTest.java b/src/test/java/nextstep/courses/domain/ImageTypeTest.java
index 1a23bdcfa..27e530a32 100644
--- a/src/test/java/nextstep/courses/domain/ImageTypeTest.java
+++ b/src/test/java/nextstep/courses/domain/ImageTypeTest.java
@@ -5,10 +5,18 @@
 import org.junit.jupiter.api.DisplayNameGeneration;
 import org.junit.jupiter.api.DisplayNameGenerator;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
 
 @DisplayNameGeneration(DisplayNameGenerator.ReplaceUnderscores.class)
 class ImageTypeTest {
 
+    @ParameterizedTest(name = "입력값:{0}")
+    @ValueSource(strings = {"png", "PNG"})
+    void from_정상입력_변환성공(String input) {
+        assertThat(ImageType.from(input)).isEqualTo(ImageType.PNG);
+    }
+
     @Test
     void from_JPEG입력_JPG반환() {
         assertThat(ImageType.from("jpeg")).isEqualTo(ImageType.JPG);

From 5ce49fc22b302f51d193b8b88db4e63669b70c67 Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 06:39:00 +0900
Subject: [PATCH 05/45] =?UTF-8?q?feat:=20CoverImage=20=EB=8F=84=EB=A9=94?=
 =?UTF-8?q?=EC=9D=B8=20=EC=B6=94=EA=B0=80=20=EB=B0=8F=20=ED=8C=8C=EC=9D=BC?=
 =?UTF-8?q?=20=ED=81=AC=EA=B8=B0=20=EA=B2=80=EC=A6=9D=20=EB=A1=9C=EC=A7=81?=
 =?UTF-8?q?=20=EA=B5=AC=ED=98=84?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

CoverImage.java
- CoverImage 도메인 클래스 신규 추가
- 파일 크기 최대 1MB 제한 상수 정의
- 생성 시 파일 크기 검증 수행
- 검증 실패 시 IllegalArgumentException 발생하도록 구현

CoverImageTest.java
- 정상 생성 테스트 추가
- 파일 크기 초과 시 예외 발생 테스트 추가
---
 .../nextstep/courses/domain/CoverImage.java   | 25 +++++++++++++++++++
 .../courses/domain/CoverImageTest.java        | 25 +++++++++++++++++++
 2 files changed, 50 insertions(+)
 create mode 100644 src/main/java/nextstep/courses/domain/CoverImage.java
 create mode 100644 src/test/java/nextstep/courses/domain/CoverImageTest.java

diff --git a/src/main/java/nextstep/courses/domain/CoverImage.java b/src/main/java/nextstep/courses/domain/CoverImage.java
new file mode 100644
index 000000000..f0fa69d34
--- /dev/null
+++ b/src/main/java/nextstep/courses/domain/CoverImage.java
@@ -0,0 +1,25 @@
+package nextstep.courses.domain;
+
+public class CoverImage {
+    private static final long MAX_FILE_SIZE = 1024 * 1024;
+
+    private String filename;
+    private long fileSize;
+    private ImageType imageType;
+    private int width;
+    private int height;
+
+    public CoverImage(String filename, long fileSize, ImageType imageType, int width, int height) {
+        validateFileSize(fileSize);
+        this.filename = filename;
+        this.fileSize = fileSize;
+        this.imageType = imageType;
+        this.width = width;
+        this.height = height;
+    }
+
+    private void validateFileSize(long fileSize) {
+        if (fileSize > MAX_FILE_SIZE)
+            throw new IllegalArgumentException("이미지 크기는 1MB 이하여야 합니다. (입력: %d bytes)", fileSize);
+    }
+}
diff --git a/src/test/java/nextstep/courses/domain/CoverImageTest.java b/src/test/java/nextstep/courses/domain/CoverImageTest.java
new file mode 100644
index 000000000..ba26d71d5
--- /dev/null
+++ b/src/test/java/nextstep/courses/domain/CoverImageTest.java
@@ -0,0 +1,25 @@
+package nextstep.courses.domain;
+
+import static org.assertj.core.api.Assertions.*;
+
+import org.junit.jupiter.api.DisplayNameGeneration;
+import org.junit.jupiter.api.DisplayNameGenerator;
+import org.junit.jupiter.api.Test;
+
+@DisplayNameGeneration(DisplayNameGenerator.ReplaceUnderscores.class)
+class CoverImageTest {
+
+    @Test
+    void 생성자_정상입력_생성성공() {
+        assertThatCode(() -> new CoverImage("image.png", 1024 * 1024, ImageType.PNG, 300, 200))
+                .doesNotThrowAnyException();
+    }
+
+    @Test
+    void 생성자_파일크기초과_예외발생() {
+        long overSize = 1024 * 1024 + 1;
+        assertThatThrownBy(() -> new CoverImage("image.png", overSize, ImageType.PNG, 300, 200))
+                .isInstanceOf(IllegalArgumentException.class)
+                .hasMessageContaining("이미지 크기는 1MB 이하여야 합니다.");
+    }
+}

From ae72cccad08050e7164b9563110c0c0d83c9afa6 Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 06:46:06 +0900
Subject: [PATCH 06/45] =?UTF-8?q?feat:=20CoverImage=EC=97=90=20=EC=B5=9C?=
 =?UTF-8?q?=EC=86=8C=20=ED=95=B4=EC=83=81=EB=8F=84=20=EA=B2=80=EC=A6=9D=20?=
 =?UTF-8?q?=EC=B6=94=EA=B0=80?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

CoverImage.java
- 최소 너비/높이 상수(MIN_WIDTH=300, MIN_HEIGHT=200) 추가
- 생성 시 validateDimension 호출하여 해상도 검증 추가
- 너비/높이 부족 시 상세 메시지 포함 예외 발생

CoverImageTest.java
- 너비 부족 시 예외 발생 테스트 추가
- 높이 부족 시 예외 발생 테스트 추가
---
 .../java/nextstep/courses/domain/CoverImage.java   | 14 +++++++++++++-
 .../nextstep/courses/domain/CoverImageTest.java    | 14 ++++++++++++++
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/src/main/java/nextstep/courses/domain/CoverImage.java b/src/main/java/nextstep/courses/domain/CoverImage.java
index f0fa69d34..434f2511b 100644
--- a/src/main/java/nextstep/courses/domain/CoverImage.java
+++ b/src/main/java/nextstep/courses/domain/CoverImage.java
@@ -2,6 +2,8 @@
 
 public class CoverImage {
     private static final long MAX_FILE_SIZE = 1024 * 1024;
+    private static final int MIN_WIDTH = 300;
+    private static final int MIN_HEIGHT = 200;
 
     private String filename;
     private long fileSize;
@@ -11,6 +13,7 @@ public class CoverImage {
 
     public CoverImage(String filename, long fileSize, ImageType imageType, int width, int height) {
         validateFileSize(fileSize);
+        validateDimension(width, height);
         this.filename = filename;
         this.fileSize = fileSize;
         this.imageType = imageType;
@@ -20,6 +23,15 @@ public CoverImage(String filename, long fileSize, ImageType imageType, int width
 
     private void validateFileSize(long fileSize) {
         if (fileSize > MAX_FILE_SIZE)
-            throw new IllegalArgumentException("이미지 크기는 1MB 이하여야 합니다. (입력: %d bytes)", fileSize);
+            throw new IllegalArgumentException(String.format("이미지 크기는 1MB 이하여야 합니다. (입력: %d bytes)", fileSize));
+    }
+
+    private void validateDimension(int width, int height) {
+        if (width < MIN_WIDTH) {
+            throw new IllegalArgumentException(String.format("이미지 너비는 %d픽셀 이상이어야 합니다. (입력: %d)", MIN_WIDTH, width));
+        }
+        if (height < MIN_HEIGHT) {
+            throw new IllegalArgumentException(String.format("이미지 높이는 %d픽셀 이상이어야 합니다. (입력: %d)", MIN_HEIGHT, height));
+        }
     }
 }
diff --git a/src/test/java/nextstep/courses/domain/CoverImageTest.java b/src/test/java/nextstep/courses/domain/CoverImageTest.java
index ba26d71d5..b9747cb42 100644
--- a/src/test/java/nextstep/courses/domain/CoverImageTest.java
+++ b/src/test/java/nextstep/courses/domain/CoverImageTest.java
@@ -22,4 +22,18 @@ class CoverImageTest {
                 .isInstanceOf(IllegalArgumentException.class)
                 .hasMessageContaining("이미지 크기는 1MB 이하여야 합니다.");
     }
+
+    @Test
+    void 생성_너비부족_예외발생() {
+        assertThatThrownBy(() -> new CoverImage("image.png", 1024, ImageType.PNG, 299, 200))
+                .isInstanceOf(IllegalArgumentException.class)
+                .hasMessageContaining("너비는 300픽셀 이상");
+    }
+
+    @Test
+    void 생성_높이부족_예외발생() {
+        assertThatThrownBy(() -> new CoverImage("image.png", 1024, ImageType.PNG, 300, 199))
+                .isInstanceOf(IllegalArgumentException.class)
+                .hasMessageContaining("높이는 200픽셀 이상");
+    }
 }

From 44cfb1ccb9df2eb185eefa9a4f8ca1a6074bdb05 Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 06:48:28 +0900
Subject: [PATCH 07/45] =?UTF-8?q?feat:=20CoverImage=EC=97=90=20=EC=9D=B4?=
 =?UTF-8?q?=EB=AF=B8=EC=A7=80=20=EB=B9=84=EC=9C=A8(3:2)=20=EA=B2=80?=
 =?UTF-8?q?=EC=A6=9D=20=EC=B6=94=EA=B0=80?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

CoverImage.java
- WIDTH_RATIO=3, HEIGHT_RATIO=2 상수 추가
- 생성 시 validateAspectRatio 실행하도록 추가
- 비율 불일치 시 상세 메시지 포함 예외 발생

CoverImageTest.java
- 3:2 비율이 아닐 경우 예외 발생 테스트 추가
---
 src/main/java/nextstep/courses/domain/CoverImage.java    | 9 +++++++++
 .../java/nextstep/courses/domain/CoverImageTest.java     | 7 +++++++
 2 files changed, 16 insertions(+)

diff --git a/src/main/java/nextstep/courses/domain/CoverImage.java b/src/main/java/nextstep/courses/domain/CoverImage.java
index 434f2511b..1a9d7b1b7 100644
--- a/src/main/java/nextstep/courses/domain/CoverImage.java
+++ b/src/main/java/nextstep/courses/domain/CoverImage.java
@@ -4,6 +4,8 @@ public class CoverImage {
     private static final long MAX_FILE_SIZE = 1024 * 1024;
     private static final int MIN_WIDTH = 300;
     private static final int MIN_HEIGHT = 200;
+    private static final int WIDTH_RATIO = 3;
+    private static final int HEIGHT_RATIO = 2;
 
     private String filename;
     private long fileSize;
@@ -14,6 +16,7 @@ public class CoverImage {
     public CoverImage(String filename, long fileSize, ImageType imageType, int width, int height) {
         validateFileSize(fileSize);
         validateDimension(width, height);
+        validateAspectRatio(width, height);
         this.filename = filename;
         this.fileSize = fileSize;
         this.imageType = imageType;
@@ -34,4 +37,10 @@ private void validateDimension(int width, int height) {
             throw new IllegalArgumentException(String.format("이미지 높이는 %d픽셀 이상이어야 합니다. (입력: %d)", MIN_HEIGHT, height));
         }
     }
+
+    private void validateAspectRatio(int width, int height) {
+        if (width * HEIGHT_RATIO != height * WIDTH_RATIO) {
+            throw new IllegalArgumentException(String.format("이미지 비율은 3:2여야 합니다. (입력: %d:%d)", width, height));
+        }
+    }
 }
diff --git a/src/test/java/nextstep/courses/domain/CoverImageTest.java b/src/test/java/nextstep/courses/domain/CoverImageTest.java
index b9747cb42..2169ae305 100644
--- a/src/test/java/nextstep/courses/domain/CoverImageTest.java
+++ b/src/test/java/nextstep/courses/domain/CoverImageTest.java
@@ -36,4 +36,11 @@ class CoverImageTest {
                 .isInstanceOf(IllegalArgumentException.class)
                 .hasMessageContaining("높이는 200픽셀 이상");
     }
+
+    @Test
+    void 생성_비율불일치_예외발생() {
+        assertThatThrownBy(() -> new CoverImage("image.png", 1024, ImageType.PNG, 300, 300))
+                .isInstanceOf(IllegalArgumentException.class)
+                .hasMessageContaining("비율은 3:2");
+    }
 }

From 87608e0a0061dd5992599fe7ba54f561c4fa5a55 Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 06:52:50 +0900
Subject: [PATCH 08/45] =?UTF-8?q?feat:=20CoverImage=EC=97=90=20=ED=99=95?=
 =?UTF-8?q?=EC=9E=A5=EC=9E=90=20=EC=9E=90=EB=8F=99=20=EC=B6=94=EC=B6=9C=20?=
 =?UTF-8?q?=EB=B0=8F=20=EA=B2=80=EC=A6=9D=20=EB=A1=9C=EC=A7=81=20=EC=B6=94?=
 =?UTF-8?q?=EA=B0=80?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

CoverImage.java
- filename 기반으로 확장자를 추출해 ImageType을 자동 결정하는 생성자 추가
- extractExtension 메서드 추가하여 확장자 누락/잘못된 형식 검증
- 기존 생성자 로직과 동일하게 파일 크기·해상도·비율 검증 수행

CoverImageTest.java
- 확장자 미존재 시 예외 발생 테스트 추가
---
 .../java/nextstep/courses/domain/CoverImage.java     | 12 ++++++++++++
 .../java/nextstep/courses/domain/CoverImageTest.java |  7 +++++++
 2 files changed, 19 insertions(+)

diff --git a/src/main/java/nextstep/courses/domain/CoverImage.java b/src/main/java/nextstep/courses/domain/CoverImage.java
index 1a9d7b1b7..be4a411cf 100644
--- a/src/main/java/nextstep/courses/domain/CoverImage.java
+++ b/src/main/java/nextstep/courses/domain/CoverImage.java
@@ -13,6 +13,10 @@ public class CoverImage {
     private int width;
     private int height;
 
+    public CoverImage(String filename, long fileSize, int width, int height) {
+        this(filename, fileSize, ImageType.from(extractExtension(filename)), width, height);
+    }
+
     public CoverImage(String filename, long fileSize, ImageType imageType, int width, int height) {
         validateFileSize(fileSize);
         validateDimension(width, height);
@@ -24,6 +28,14 @@ public CoverImage(String filename, long fileSize, ImageType imageType, int width
         this.height = height;
     }
 
+    private static String extractExtension(String filename) {
+        int dotIndex = filename.lastIndexOf('.');
+        if (dotIndex == -1 || dotIndex == filename.length() - 1) {
+            throw new IllegalArgumentException("파일 확장자가 없습니다. (입력: " + filename + ")");
+        }
+        return filename.substring(dotIndex + 1);
+    }
+
     private void validateFileSize(long fileSize) {
         if (fileSize > MAX_FILE_SIZE)
             throw new IllegalArgumentException(String.format("이미지 크기는 1MB 이하여야 합니다. (입력: %d bytes)", fileSize));
diff --git a/src/test/java/nextstep/courses/domain/CoverImageTest.java b/src/test/java/nextstep/courses/domain/CoverImageTest.java
index 2169ae305..8cbcccfd6 100644
--- a/src/test/java/nextstep/courses/domain/CoverImageTest.java
+++ b/src/test/java/nextstep/courses/domain/CoverImageTest.java
@@ -23,6 +23,13 @@ class CoverImageTest {
                 .hasMessageContaining("이미지 크기는 1MB 이하여야 합니다.");
     }
 
+    @Test
+    void 생성_확장자없음_예외발생() {
+        assertThatThrownBy(() -> new CoverImage("image", 1024, 300, 200))
+                .isInstanceOf(IllegalArgumentException.class)
+                .hasMessageContaining("파일 확장자가 없습니다");
+    }
+
     @Test
     void 생성_너비부족_예외발생() {
         assertThatThrownBy(() -> new CoverImage("image.png", 1024, ImageType.PNG, 299, 200))

From 95a274cd16cfa75250683b8ebbb63e59efb43fa0 Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 07:13:01 +0900
Subject: [PATCH 09/45] =?UTF-8?q?feat:=20=EC=9D=B4=EB=AF=B8=EC=A7=80=20?=
 =?UTF-8?q?=ED=95=B4=EC=83=81=EB=8F=84=20=EC=A0=84=EC=9A=A9=20Value=20Obje?=
 =?UTF-8?q?ct=20ImageDimension=20=EC=B6=94=EA=B0=80?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

ImageDimension.java
- 최소 너비(300), 최소 높이(200), 비율(3:2) 검증 로직 포함한 VO 추가
- 생성 시 해상도 조건 및 비율 조건 유효성 검증 수행
- width, height 불변 값으로 보관

ImageDimensionTest.java
- 정상 생성 테스트 추가
- 너비 부족, 높이 부족, 비율 불일치 경우 각각 예외 검증 테스트 추가
---
 .../courses/domain/ImageDimension.java        | 33 +++++++++++++++++
 .../courses/domain/ImageDimensionTest.java    | 36 +++++++++++++++++++
 2 files changed, 69 insertions(+)
 create mode 100644 src/main/java/nextstep/courses/domain/ImageDimension.java
 create mode 100644 src/test/java/nextstep/courses/domain/ImageDimensionTest.java

diff --git a/src/main/java/nextstep/courses/domain/ImageDimension.java b/src/main/java/nextstep/courses/domain/ImageDimension.java
new file mode 100644
index 000000000..80684887c
--- /dev/null
+++ b/src/main/java/nextstep/courses/domain/ImageDimension.java
@@ -0,0 +1,33 @@
+package nextstep.courses.domain;
+
+public class ImageDimension {
+    private static final int MIN_WIDTH = 300;
+    private static final int MIN_HEIGHT = 200;
+    private static final int WIDTH_RATIO = 3;
+    private static final int HEIGHT_RATIO = 2;
+
+    private final int width;
+    private final int height;
+
+    public ImageDimension(int width, int height) {
+        validateDimension(width, height);
+        validateAspectRatio(width, height);
+        this.width = width;
+        this.height = height;
+    }
+
+    private void validateDimension(int width, int height) {
+        if (width < MIN_WIDTH) {
+            throw new IllegalArgumentException(String.format("이미지 너비는 %d픽셀 이상이어야 합니다. (입력: %d)", MIN_WIDTH, width));
+        }
+        if (height < MIN_HEIGHT) {
+            throw new IllegalArgumentException(String.format("이미지 높이는 %d픽셀 이상이어야 합니다. (입력: %d)", MIN_HEIGHT, height));
+        }
+    }
+
+    private void validateAspectRatio(int width, int height) {
+        if (width * HEIGHT_RATIO != height * WIDTH_RATIO) {
+            throw new IllegalArgumentException(String.format("이미지 비율은 3:2여야 합니다. (입력: %d:%d)", width, height));
+        }
+    }
+}
diff --git a/src/test/java/nextstep/courses/domain/ImageDimensionTest.java b/src/test/java/nextstep/courses/domain/ImageDimensionTest.java
new file mode 100644
index 000000000..8ec352bef
--- /dev/null
+++ b/src/test/java/nextstep/courses/domain/ImageDimensionTest.java
@@ -0,0 +1,36 @@
+package nextstep.courses.domain;
+
+import static org.assertj.core.api.Assertions.*;
+
+import org.junit.jupiter.api.DisplayNameGeneration;
+import org.junit.jupiter.api.DisplayNameGenerator;
+import org.junit.jupiter.api.Test;
+
+@DisplayNameGeneration(DisplayNameGenerator.ReplaceUnderscores.class)
+class ImageDimensionTest {
+    @Test
+    void 생성_정상입력_생성성공() {
+        assertThatCode(() -> new ImageDimension(300, 200)).doesNotThrowAnyException();
+    }
+
+    @Test
+    void 생성_너비부족_예외발생() {
+        assertThatThrownBy(() -> new ImageDimension(299, 200))
+                .isInstanceOf(IllegalArgumentException.class)
+                .hasMessageContaining("너비는 300픽셀 이상");
+    }
+
+    @Test
+    void 생성_높이부족_예외발생() {
+        assertThatThrownBy(() -> new ImageDimension(300, 199))
+                .isInstanceOf(IllegalArgumentException.class)
+                .hasMessageContaining("높이는 200픽셀 이상");
+    }
+
+    @Test
+    void 생성_비율불일치_예외발생() {
+        assertThatThrownBy(() -> new ImageDimension(300, 300))
+                .isInstanceOf(IllegalArgumentException.class)
+                .hasMessageContaining("비율은 3:2");
+    }
+}

From 282297fc32434c4b02f18b8061bcda05bbaa48f2 Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 07:15:46 +0900
Subject: [PATCH 10/45] =?UTF-8?q?feat:=20=EC=9D=B4=EB=AF=B8=EC=A7=80=20?=
 =?UTF-8?q?=ED=8C=8C=EC=9D=BC=20=EC=A0=84=EC=9A=A9=20Value=20Object=20Imag?=
 =?UTF-8?q?eFile=20=EC=B6=94=EA=B0=80?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

ImageFile.java
- 파일 크기 최대 1MB 제한 검증 추가
- 파일명에서 확장자를 추출하여 ImageType 자동 매핑
- 확장자 없음 또는 빈 확장자일 경우 예외 발생

ImageFileTest.java
- 정상 생성 테스트 추가
- 파일 크기 초과 시 예외 발생 테스트 추가
- 확장자 누락 시 예외 발생 테스트 추가
---
 .../nextstep/courses/domain/ImageFile.java    | 30 ++++++++++++++++++
 .../courses/domain/ImageFileTest.java         | 31 +++++++++++++++++++
 2 files changed, 61 insertions(+)
 create mode 100644 src/main/java/nextstep/courses/domain/ImageFile.java
 create mode 100644 src/test/java/nextstep/courses/domain/ImageFileTest.java

diff --git a/src/main/java/nextstep/courses/domain/ImageFile.java b/src/main/java/nextstep/courses/domain/ImageFile.java
new file mode 100644
index 000000000..8baf8f463
--- /dev/null
+++ b/src/main/java/nextstep/courses/domain/ImageFile.java
@@ -0,0 +1,30 @@
+package nextstep.courses.domain;
+
+public class ImageFile {
+    private static final long MAX_FILE_SIZE = 1024 * 1024;
+
+    private final String filename;
+    private final long fileSize;
+    private final ImageType imageType;
+
+    public ImageFile(String filename, long fileSize) {
+        validateFileSize(fileSize);
+        this.filename = filename;
+        this.fileSize = fileSize;
+        this.imageType = ImageType.from(extractExtension(filename));
+    }
+
+    private void validateFileSize(long fileSize) {
+        if (fileSize > MAX_FILE_SIZE) {
+            throw new IllegalArgumentException(String.format("이미지 크기는 1MB 이하여야 합니다. (입력: %d bytes)", fileSize));
+        }
+    }
+
+    private String extractExtension(String filename) {
+        int dotIndex = filename.lastIndexOf('.');
+        if (dotIndex == -1 || dotIndex == filename.length() - 1) {
+            throw new IllegalArgumentException("파일 확장자가 없습니다. (입력: " + filename + ")");
+        }
+        return filename.substring(dotIndex + 1);
+    }
+}
diff --git a/src/test/java/nextstep/courses/domain/ImageFileTest.java b/src/test/java/nextstep/courses/domain/ImageFileTest.java
new file mode 100644
index 000000000..c82306408
--- /dev/null
+++ b/src/test/java/nextstep/courses/domain/ImageFileTest.java
@@ -0,0 +1,31 @@
+package nextstep.courses.domain;
+
+import static org.assertj.core.api.Assertions.*;
+
+import org.junit.jupiter.api.DisplayNameGeneration;
+import org.junit.jupiter.api.DisplayNameGenerator;
+import org.junit.jupiter.api.Test;
+
+@DisplayNameGeneration(DisplayNameGenerator.ReplaceUnderscores.class)
+class ImageFileTest {
+    @Test
+    void 생성_정상입력_생성성공() {
+        assertThatCode(() -> new ImageFile("image.png", 1024 * 1024)).doesNotThrowAnyException();
+    }
+
+    @Test
+    void 생성_파일크기초과_예외발생() {
+        long overSize = 1024 * 1024 + 1;
+
+        assertThatThrownBy(() -> new ImageFile("image.png", overSize))
+                .isInstanceOf(IllegalArgumentException.class)
+                .hasMessageContaining("이미지 크기는 1MB 이하여야 합니다.");
+    }
+
+    @Test
+    void 생성_확장자없음_예외발생() {
+        assertThatThrownBy(() -> new ImageFile("image", 1024 * 1024))
+                .isInstanceOf(IllegalArgumentException.class)
+                .hasMessageContaining("파일 확장자가 없습니다");
+    }
+}

From de23c2a47559016e508fef82b258ed118f16f2f2 Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 07:18:38 +0900
Subject: [PATCH 11/45] =?UTF-8?q?refactor:=20CoverImage=EB=A5=BC=20ImageFi?=
 =?UTF-8?q?le=C2=B7ImageDimension=20VO=20=EC=A1=B0=ED=95=A9=20=EA=B5=AC?=
 =?UTF-8?q?=EC=A1=B0=EB=A1=9C=20=EB=8B=A8=EC=88=9C=ED=99=94?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

CoverImage.java
- 파일 검증 → ImageFile로 위임
- 해상도·비율 검증 → ImageDimension으로 위임
- CoverImage는 두 VO를 구성요소로 보유하도록 변경
- 기존 개별 검증 로직 및 생성자 삭제

CoverImageTest.java
- 파일/해상도/비율 검증 책임이 개별 VO로 이동함에 따라 테스트 제거
---
 .../nextstep/courses/domain/CoverImage.java   | 55 ++-----------------
 .../courses/domain/CoverImageTest.java        | 53 ------------------
 2 files changed, 4 insertions(+), 104 deletions(-)
 delete mode 100644 src/test/java/nextstep/courses/domain/CoverImageTest.java

diff --git a/src/main/java/nextstep/courses/domain/CoverImage.java b/src/main/java/nextstep/courses/domain/CoverImage.java
index be4a411cf..62c15cc39 100644
--- a/src/main/java/nextstep/courses/domain/CoverImage.java
+++ b/src/main/java/nextstep/courses/domain/CoverImage.java
@@ -1,58 +1,11 @@
 package nextstep.courses.domain;
 
 public class CoverImage {
-    private static final long MAX_FILE_SIZE = 1024 * 1024;
-    private static final int MIN_WIDTH = 300;
-    private static final int MIN_HEIGHT = 200;
-    private static final int WIDTH_RATIO = 3;
-    private static final int HEIGHT_RATIO = 2;
-
-    private String filename;
-    private long fileSize;
-    private ImageType imageType;
-    private int width;
-    private int height;
+    private final ImageFile imageFile;
+    private final ImageDimension dimension;
 
     public CoverImage(String filename, long fileSize, int width, int height) {
-        this(filename, fileSize, ImageType.from(extractExtension(filename)), width, height);
-    }
-
-    public CoverImage(String filename, long fileSize, ImageType imageType, int width, int height) {
-        validateFileSize(fileSize);
-        validateDimension(width, height);
-        validateAspectRatio(width, height);
-        this.filename = filename;
-        this.fileSize = fileSize;
-        this.imageType = imageType;
-        this.width = width;
-        this.height = height;
-    }
-
-    private static String extractExtension(String filename) {
-        int dotIndex = filename.lastIndexOf('.');
-        if (dotIndex == -1 || dotIndex == filename.length() - 1) {
-            throw new IllegalArgumentException("파일 확장자가 없습니다. (입력: " + filename + ")");
-        }
-        return filename.substring(dotIndex + 1);
-    }
-
-    private void validateFileSize(long fileSize) {
-        if (fileSize > MAX_FILE_SIZE)
-            throw new IllegalArgumentException(String.format("이미지 크기는 1MB 이하여야 합니다. (입력: %d bytes)", fileSize));
-    }
-
-    private void validateDimension(int width, int height) {
-        if (width < MIN_WIDTH) {
-            throw new IllegalArgumentException(String.format("이미지 너비는 %d픽셀 이상이어야 합니다. (입력: %d)", MIN_WIDTH, width));
-        }
-        if (height < MIN_HEIGHT) {
-            throw new IllegalArgumentException(String.format("이미지 높이는 %d픽셀 이상이어야 합니다. (입력: %d)", MIN_HEIGHT, height));
-        }
-    }
-
-    private void validateAspectRatio(int width, int height) {
-        if (width * HEIGHT_RATIO != height * WIDTH_RATIO) {
-            throw new IllegalArgumentException(String.format("이미지 비율은 3:2여야 합니다. (입력: %d:%d)", width, height));
-        }
+        this.imageFile = new ImageFile(filename, fileSize);
+        this.dimension = new ImageDimension(width, height);
     }
 }
diff --git a/src/test/java/nextstep/courses/domain/CoverImageTest.java b/src/test/java/nextstep/courses/domain/CoverImageTest.java
deleted file mode 100644
index 8cbcccfd6..000000000
--- a/src/test/java/nextstep/courses/domain/CoverImageTest.java
+++ /dev/null
@@ -1,53 +0,0 @@
-package nextstep.courses.domain;
-
-import static org.assertj.core.api.Assertions.*;
-
-import org.junit.jupiter.api.DisplayNameGeneration;
-import org.junit.jupiter.api.DisplayNameGenerator;
-import org.junit.jupiter.api.Test;
-
-@DisplayNameGeneration(DisplayNameGenerator.ReplaceUnderscores.class)
-class CoverImageTest {
-
-    @Test
-    void 생성자_정상입력_생성성공() {
-        assertThatCode(() -> new CoverImage("image.png", 1024 * 1024, ImageType.PNG, 300, 200))
-                .doesNotThrowAnyException();
-    }
-
-    @Test
-    void 생성자_파일크기초과_예외발생() {
-        long overSize = 1024 * 1024 + 1;
-        assertThatThrownBy(() -> new CoverImage("image.png", overSize, ImageType.PNG, 300, 200))
-                .isInstanceOf(IllegalArgumentException.class)
-                .hasMessageContaining("이미지 크기는 1MB 이하여야 합니다.");
-    }
-
-    @Test
-    void 생성_확장자없음_예외발생() {
-        assertThatThrownBy(() -> new CoverImage("image", 1024, 300, 200))
-                .isInstanceOf(IllegalArgumentException.class)
-                .hasMessageContaining("파일 확장자가 없습니다");
-    }
-
-    @Test
-    void 생성_너비부족_예외발생() {
-        assertThatThrownBy(() -> new CoverImage("image.png", 1024, ImageType.PNG, 299, 200))
-                .isInstanceOf(IllegalArgumentException.class)
-                .hasMessageContaining("너비는 300픽셀 이상");
-    }
-
-    @Test
-    void 생성_높이부족_예외발생() {
-        assertThatThrownBy(() -> new CoverImage("image.png", 1024, ImageType.PNG, 300, 199))
-                .isInstanceOf(IllegalArgumentException.class)
-                .hasMessageContaining("높이는 200픽셀 이상");
-    }
-
-    @Test
-    void 생성_비율불일치_예외발생() {
-        assertThatThrownBy(() -> new CoverImage("image.png", 1024, ImageType.PNG, 300, 300))
-                .isInstanceOf(IllegalArgumentException.class)
-                .hasMessageContaining("비율은 3:2");
-    }
-}

From 4c31460aff40589cb586b480061a11a965f9e64f Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 07:24:37 +0900
Subject: [PATCH 12/45] =?UTF-8?q?feat:=20SessionStatus=20=EC=B6=94?=
 =?UTF-8?q?=EA=B0=80=20=EB=B0=8F=20=EC=88=98=EA=B0=95=EC=8B=A0=EC=B2=AD=20?=
 =?UTF-8?q?=EA=B0=80=EB=8A=A5=20=EC=97=AC=EB=B6=80=20=ED=8C=90=EB=8B=A8=20?=
 =?UTF-8?q?=EB=A1=9C=EC=A7=81=20=EA=B5=AC=ED=98=84?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

SessionStatus.java
- PREPARING, RECRUITING, CLOSED 상태 enum 정의
- 상태별 설명 필드 추가
- 모집중(RECRUITING)일 때만 수강신청 가능하도록 canEnroll() 메서드 구현

SessionStatusTest.java
- 준비중/종료 상태에서는 신청 불가, 모집중일 때만 신청 가능함을 검증하는 테스트 추가
---
 .../courses/domain/SessionStatus.java         | 17 ++++++++++++
 .../courses/domain/SessionStatusTest.java     | 26 +++++++++++++++++++
 2 files changed, 43 insertions(+)
 create mode 100644 src/main/java/nextstep/courses/domain/SessionStatus.java
 create mode 100644 src/test/java/nextstep/courses/domain/SessionStatusTest.java

diff --git a/src/main/java/nextstep/courses/domain/SessionStatus.java b/src/main/java/nextstep/courses/domain/SessionStatus.java
new file mode 100644
index 000000000..6a535e5be
--- /dev/null
+++ b/src/main/java/nextstep/courses/domain/SessionStatus.java
@@ -0,0 +1,17 @@
+package nextstep.courses.domain;
+
+public enum SessionStatus {
+    PREPARING("준비중"),
+    RECRUITING("모집중"),
+    CLOSED("종료");
+
+    SessionStatus(String description) {
+        this.description = description;
+    }
+
+    private final String description;
+
+    public boolean canEnroll() {
+        return this == RECRUITING;
+    }
+}
diff --git a/src/test/java/nextstep/courses/domain/SessionStatusTest.java b/src/test/java/nextstep/courses/domain/SessionStatusTest.java
new file mode 100644
index 000000000..d4c17903d
--- /dev/null
+++ b/src/test/java/nextstep/courses/domain/SessionStatusTest.java
@@ -0,0 +1,26 @@
+package nextstep.courses.domain;
+
+import static org.assertj.core.api.Assertions.*;
+
+import org.junit.jupiter.api.DisplayNameGeneration;
+import org.junit.jupiter.api.DisplayNameGenerator;
+import org.junit.jupiter.api.Test;
+
+@DisplayNameGeneration(DisplayNameGenerator.ReplaceUnderscores.class)
+class SessionStatusTest {
+
+    @Test
+    void 준비중_수강신청불가() {
+        assertThat(SessionStatus.PREPARING.canEnroll()).isFalse();
+    }
+
+    @Test
+    void 모집중_수강신청가능() {
+        assertThat(SessionStatus.RECRUITING.canEnroll()).isTrue();
+    }
+
+    @Test
+    void 종료_수강신청불가() {
+        assertThat(SessionStatus.CLOSED.canEnroll()).isFalse();
+    }
+}

From 6f596756c1e7903424c88fe10cde312351c527ce Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 07:27:29 +0900
Subject: [PATCH 13/45] =?UTF-8?q?feat:=20SessionPeriod=20=EA=B0=92=20?=
 =?UTF-8?q?=EA=B0=9D=EC=B2=B4=20=EC=B6=94=EA=B0=80?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

SessionPeriod.java
- 시작일·종료일을 표현하는 VO 추가
- 종료일이 시작일보다 이전일 경우 예외 발생하도록 검증 로직 구현

SessionPeriodTest.java
- 정상 생성 테스트 추가
- 종료일 < 시작일일 때 예외 발생 테스트 추가
---
 .../courses/domain/SessionPeriod.java         | 21 ++++++++++++++
 .../courses/domain/SessionPeriodTest.java     | 29 +++++++++++++++++++
 2 files changed, 50 insertions(+)
 create mode 100644 src/main/java/nextstep/courses/domain/SessionPeriod.java
 create mode 100644 src/test/java/nextstep/courses/domain/SessionPeriodTest.java

diff --git a/src/main/java/nextstep/courses/domain/SessionPeriod.java b/src/main/java/nextstep/courses/domain/SessionPeriod.java
new file mode 100644
index 000000000..aafa7fb58
--- /dev/null
+++ b/src/main/java/nextstep/courses/domain/SessionPeriod.java
@@ -0,0 +1,21 @@
+package nextstep.courses.domain;
+
+import java.time.LocalDate;
+
+public class SessionPeriod {
+    private final LocalDate startDate;
+    private final LocalDate endDate;
+
+    public SessionPeriod(LocalDate startDate, LocalDate endDate) {
+        validatePeriod(startDate, endDate);
+        this.startDate = startDate;
+        this.endDate = endDate;
+    }
+
+    private void validatePeriod(LocalDate startDate, LocalDate endDate) {
+        if (endDate.isBefore(startDate)) {
+            throw new IllegalArgumentException(
+                    String.format("종료일은 시작일 이후여야 합니다. (시작: %s, 종료: %s)", startDate, endDate));
+        }
+    }
+}
diff --git a/src/test/java/nextstep/courses/domain/SessionPeriodTest.java b/src/test/java/nextstep/courses/domain/SessionPeriodTest.java
new file mode 100644
index 000000000..c4f76b1be
--- /dev/null
+++ b/src/test/java/nextstep/courses/domain/SessionPeriodTest.java
@@ -0,0 +1,29 @@
+package nextstep.courses.domain;
+
+import static org.assertj.core.api.Assertions.*;
+
+import java.time.LocalDate;
+import org.junit.jupiter.api.DisplayNameGeneration;
+import org.junit.jupiter.api.DisplayNameGenerator;
+import org.junit.jupiter.api.Test;
+
+@DisplayNameGeneration(DisplayNameGenerator.ReplaceUnderscores.class)
+class SessionPeriodTest {
+    @Test
+    void 생성자_정상입력_생성성공() {
+        LocalDate start = LocalDate.of(2024, 1, 1);
+        LocalDate end = LocalDate.of(2024, 1, 2);
+
+        assertThatCode(() -> new SessionPeriod(start, end)).doesNotThrowAnyException();
+    }
+
+    @Test
+    void 생성자_종료일이시작일이전_예외발생() {
+        LocalDate start = LocalDate.of(2024, 1, 2);
+        LocalDate end = LocalDate.of(2024, 1, 1);
+
+        assertThatThrownBy(() -> new SessionPeriod(start, end))
+                .isInstanceOf(IllegalArgumentException.class)
+                .hasMessageContaining("종료일은 시작일 이후");
+    }
+}

From 658f20b791c1eccc1a2a7d3828678e8c20aaaeae Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 07:33:05 +0900
Subject: [PATCH 14/45] =?UTF-8?q?feat:=20=EA=B8=88=EC=95=A1=20=EA=B0=92=20?=
 =?UTF-8?q?=EA=B0=9D=EC=B2=B4=20Money=20=EC=B6=94=EA=B0=80?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Money.java
- 음수 금액을 허용하지 않는 Money VO 추가
- 0 이상인지 검증하는 validate 로직 구현

MoneyTest.java
- 0 및 양수 입력 시 정상 생성 테스트 추가
- 음수 입력 시 예외 발생 테스트 추가
---
 .../java/nextstep/courses/domain/Money.java   | 14 ++++++++++
 .../nextstep/courses/domain/MoneyTest.java    | 26 +++++++++++++++++++
 2 files changed, 40 insertions(+)
 create mode 100644 src/main/java/nextstep/courses/domain/Money.java
 create mode 100644 src/test/java/nextstep/courses/domain/MoneyTest.java

diff --git a/src/main/java/nextstep/courses/domain/Money.java b/src/main/java/nextstep/courses/domain/Money.java
new file mode 100644
index 000000000..2fa73ebf7
--- /dev/null
+++ b/src/main/java/nextstep/courses/domain/Money.java
@@ -0,0 +1,14 @@
+package nextstep.courses.domain;
+
+public class Money {
+    private final int value;
+
+    public Money(int value) {
+        validate(value);
+        this.value = value;
+    }
+
+    private static void validate(int value) {
+        if (value < 0) throw new IllegalArgumentException(String.format("금액은 0 이상이어야 합니다. (입력: %d)", value));
+    }
+}
diff --git a/src/test/java/nextstep/courses/domain/MoneyTest.java b/src/test/java/nextstep/courses/domain/MoneyTest.java
new file mode 100644
index 000000000..738e6fbba
--- /dev/null
+++ b/src/test/java/nextstep/courses/domain/MoneyTest.java
@@ -0,0 +1,26 @@
+package nextstep.courses.domain;
+
+import static org.assertj.core.api.Assertions.*;
+
+import org.junit.jupiter.api.DisplayNameGeneration;
+import org.junit.jupiter.api.DisplayNameGenerator;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
+
+@DisplayNameGeneration(DisplayNameGenerator.ReplaceUnderscores.class)
+class MoneyTest {
+
+    @ParameterizedTest(name = "입력값:{0}")
+    @ValueSource(ints = {0, 10000})
+    void 생성자_정상입력_생성성공(int input) {
+        assertThatCode(() -> new Money(input)).doesNotThrowAnyException();
+    }
+
+    @Test
+    void 생성자_음수금액_예외발생() {
+        assertThatThrownBy(() -> new Money(-1))
+                .isInstanceOf(IllegalArgumentException.class)
+                .hasMessageContaining("금액은 0 이상");
+    }
+}

From b05d3c7b8064282f688d11a5891ed81f72b2a71d Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 07:39:23 +0900
Subject: [PATCH 15/45] =?UTF-8?q?feat:=20Money=20=EB=B9=84=EA=B5=90=20?=
 =?UTF-8?q?=EA=B8=B0=EB=8A=A5=20=EC=B6=94=EA=B0=80?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Money.java
- 필드명을 value → amount로 변경하여 의미 명확화
- 동일 금액 비교를 위한 isSameAs 메서드 추가

MoneyTest.java
- isSameAs에 대한 비교 테스트(CsvSource 기반) 추가
- 동일 금액/상이한 금액에 대한 기대 결과 검증
---
 src/main/java/nextstep/courses/domain/Money.java     | 12 ++++++++----
 src/test/java/nextstep/courses/domain/MoneyTest.java | 10 ++++++++++
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/src/main/java/nextstep/courses/domain/Money.java b/src/main/java/nextstep/courses/domain/Money.java
index 2fa73ebf7..4dc3bfd7f 100644
--- a/src/main/java/nextstep/courses/domain/Money.java
+++ b/src/main/java/nextstep/courses/domain/Money.java
@@ -1,14 +1,18 @@
 package nextstep.courses.domain;
 
 public class Money {
-    private final int value;
+    private final int amount;
 
-    public Money(int value) {
-        validate(value);
-        this.value = value;
+    public Money(int amount) {
+        validate(amount);
+        this.amount = amount;
     }
 
     private static void validate(int value) {
         if (value < 0) throw new IllegalArgumentException(String.format("금액은 0 이상이어야 합니다. (입력: %d)", value));
     }
+
+    public boolean isSameAs(Money other) {
+        return this.amount == other.amount;
+    }
 }
diff --git a/src/test/java/nextstep/courses/domain/MoneyTest.java b/src/test/java/nextstep/courses/domain/MoneyTest.java
index 738e6fbba..54fd6b32e 100644
--- a/src/test/java/nextstep/courses/domain/MoneyTest.java
+++ b/src/test/java/nextstep/courses/domain/MoneyTest.java
@@ -6,6 +6,7 @@
 import org.junit.jupiter.api.DisplayNameGenerator;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
 import org.junit.jupiter.params.provider.ValueSource;
 
 @DisplayNameGeneration(DisplayNameGenerator.ReplaceUnderscores.class)
@@ -23,4 +24,13 @@ class MoneyTest {
                 .isInstanceOf(IllegalArgumentException.class)
                 .hasMessageContaining("금액은 0 이상");
     }
+
+    @ParameterizedTest(name = "금액 비교: {0} == {1} → {2}")
+    @CsvSource({"10000, 10000, true", "10000, 9999, false"})
+    void isSameAs_다른금액_비교(int amount1, int amount2, boolean expected) {
+        Money moneyA = new Money(amount1);
+        Money moneyB = new Money(amount2);
+
+        assertThat(moneyA.isSameAs(moneyB)).isEqualTo(expected);
+    }
 }

From f77c36874f12cd2c9f106f7120f56b33f44ee92d Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 07:41:16 +0900
Subject: [PATCH 16/45] =?UTF-8?q?refactor:=20=ED=85=8C=EC=8A=A4=ED=8A=B8?=
 =?UTF-8?q?=20=EB=A9=94=EC=84=9C=EB=93=9C=20=EB=AA=85=EC=9D=84=20=EC=83=9D?=
 =?UTF-8?q?=EC=84=B1=EC=9E=90/=EA=B8=B0=EB=8A=A5=20=EC=A4=91=EC=8B=AC=20?=
 =?UTF-8?q?=EB=84=A4=EC=9D=B4=EB=B0=8D=EC=9C=BC=EB=A1=9C=20=EC=A0=95?=
 =?UTF-8?q?=EB=A6=AC?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

ImageDimensionTest.java
- 테스트 메서드명을 `생성자_*` 형태로 일관되게 변경

ImageFileTest.java
- 테스트 메서드명을 `생성자_*` 형태로 일관되게 변경

SessionStatusTest.java
- canEnroll 검증 메서드명을 `canEnroll_*` 형태로 명확하게 수정
---
 .../java/nextstep/courses/domain/ImageDimensionTest.java  | 8 ++++----
 src/test/java/nextstep/courses/domain/ImageFileTest.java  | 6 +++---
 .../java/nextstep/courses/domain/SessionStatusTest.java   | 6 +++---
 3 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/src/test/java/nextstep/courses/domain/ImageDimensionTest.java b/src/test/java/nextstep/courses/domain/ImageDimensionTest.java
index 8ec352bef..9e2c00b62 100644
--- a/src/test/java/nextstep/courses/domain/ImageDimensionTest.java
+++ b/src/test/java/nextstep/courses/domain/ImageDimensionTest.java
@@ -9,26 +9,26 @@
 @DisplayNameGeneration(DisplayNameGenerator.ReplaceUnderscores.class)
 class ImageDimensionTest {
     @Test
-    void 생성_정상입력_생성성공() {
+    void 생성자_정상입력_생성성공() {
         assertThatCode(() -> new ImageDimension(300, 200)).doesNotThrowAnyException();
     }
 
     @Test
-    void 생성_너비부족_예외발생() {
+    void 생성자_너비부족_예외발생() {
         assertThatThrownBy(() -> new ImageDimension(299, 200))
                 .isInstanceOf(IllegalArgumentException.class)
                 .hasMessageContaining("너비는 300픽셀 이상");
     }
 
     @Test
-    void 생성_높이부족_예외발생() {
+    void 생성자_높이부족_예외발생() {
         assertThatThrownBy(() -> new ImageDimension(300, 199))
                 .isInstanceOf(IllegalArgumentException.class)
                 .hasMessageContaining("높이는 200픽셀 이상");
     }
 
     @Test
-    void 생성_비율불일치_예외발생() {
+    void 생성자_비율불일치_예외발생() {
         assertThatThrownBy(() -> new ImageDimension(300, 300))
                 .isInstanceOf(IllegalArgumentException.class)
                 .hasMessageContaining("비율은 3:2");
diff --git a/src/test/java/nextstep/courses/domain/ImageFileTest.java b/src/test/java/nextstep/courses/domain/ImageFileTest.java
index c82306408..e05f60c44 100644
--- a/src/test/java/nextstep/courses/domain/ImageFileTest.java
+++ b/src/test/java/nextstep/courses/domain/ImageFileTest.java
@@ -9,12 +9,12 @@
 @DisplayNameGeneration(DisplayNameGenerator.ReplaceUnderscores.class)
 class ImageFileTest {
     @Test
-    void 생성_정상입력_생성성공() {
+    void 생성자_정상입력_생성성공() {
         assertThatCode(() -> new ImageFile("image.png", 1024 * 1024)).doesNotThrowAnyException();
     }
 
     @Test
-    void 생성_파일크기초과_예외발생() {
+    void 생성자_파일크기초과_예외발생() {
         long overSize = 1024 * 1024 + 1;
 
         assertThatThrownBy(() -> new ImageFile("image.png", overSize))
@@ -23,7 +23,7 @@ class ImageFileTest {
     }
 
     @Test
-    void 생성_확장자없음_예외발생() {
+    void 생성자_확장자없음_예외발생() {
         assertThatThrownBy(() -> new ImageFile("image", 1024 * 1024))
                 .isInstanceOf(IllegalArgumentException.class)
                 .hasMessageContaining("파일 확장자가 없습니다");
diff --git a/src/test/java/nextstep/courses/domain/SessionStatusTest.java b/src/test/java/nextstep/courses/domain/SessionStatusTest.java
index d4c17903d..22f6f265c 100644
--- a/src/test/java/nextstep/courses/domain/SessionStatusTest.java
+++ b/src/test/java/nextstep/courses/domain/SessionStatusTest.java
@@ -10,17 +10,17 @@
 class SessionStatusTest {
 
     @Test
-    void 준비중_수강신청불가() {
+    void canEnroll_준비중_수강신청불가() {
         assertThat(SessionStatus.PREPARING.canEnroll()).isFalse();
     }
 
     @Test
-    void 모집중_수강신청가능() {
+    void canEnroll_모집중_수강신청가능() {
         assertThat(SessionStatus.RECRUITING.canEnroll()).isTrue();
     }
 
     @Test
-    void 종료_수강신청불가() {
+    void canEnroll_종료_수강신청불가() {
         assertThat(SessionStatus.CLOSED.canEnroll()).isFalse();
     }
 }

From 45e6e2864bfa4027b8e23ebe48e86360c8f761fd Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 07:58:03 +0900
Subject: [PATCH 17/45] =?UTF-8?q?feat:=20Session=20=EB=8F=84=EB=A9=94?=
 =?UTF-8?q?=EC=9D=B8=20=EC=B6=94=EA=B0=80?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Session.java
- Session 엔티티 신규 추가
- 기본 생성 시 상태를 PREPARING으로 설정
- 수강신청 가능 여부를 SessionStatus에 위임하여 canEnroll 구현

SessionTest.java
- 정상 생성 테스트 추가
- 기본 상태가 PREPARING인지 검증
---
 .../java/nextstep/courses/domain/Session.java | 27 +++++++++++++++++++
 .../nextstep/courses/domain/SessionTest.java  | 23 ++++++++++++++++
 2 files changed, 50 insertions(+)
 create mode 100644 src/main/java/nextstep/courses/domain/Session.java
 create mode 100644 src/test/java/nextstep/courses/domain/SessionTest.java

diff --git a/src/main/java/nextstep/courses/domain/Session.java b/src/main/java/nextstep/courses/domain/Session.java
new file mode 100644
index 000000000..b91974219
--- /dev/null
+++ b/src/main/java/nextstep/courses/domain/Session.java
@@ -0,0 +1,27 @@
+package nextstep.courses.domain;
+
+public class Session {
+    private Long id;
+    private CoverImage coverImage;
+    private SessionPeriod period;
+    private SessionStatus status;
+
+    public Session(CoverImage coverImage, SessionPeriod period) {
+        this(0L, coverImage, period, SessionStatus.PREPARING);
+    }
+
+    public Session(Long id, CoverImage coverImage, SessionPeriod period, SessionStatus status) {
+        this.id = id;
+        this.coverImage = coverImage;
+        this.period = period;
+        this.status = status;
+    }
+
+    public boolean canEnroll() {
+        return this.status.canEnroll();
+    }
+
+    public SessionStatus getStatus() {
+        return this.status;
+    }
+}
diff --git a/src/test/java/nextstep/courses/domain/SessionTest.java b/src/test/java/nextstep/courses/domain/SessionTest.java
new file mode 100644
index 000000000..a2fe7ef64
--- /dev/null
+++ b/src/test/java/nextstep/courses/domain/SessionTest.java
@@ -0,0 +1,23 @@
+package nextstep.courses.domain;
+
+import static org.assertj.core.api.Assertions.*;
+
+import java.time.LocalDate;
+import org.junit.jupiter.api.DisplayNameGeneration;
+import org.junit.jupiter.api.DisplayNameGenerator;
+import org.junit.jupiter.api.Test;
+
+@DisplayNameGeneration(DisplayNameGenerator.ReplaceUnderscores.class)
+class SessionTest {
+
+    @Test
+    void 생성자_정상입력_생성성공() {
+        CoverImage coverImage = new CoverImage("image.png", 1024, 300, 200);
+        SessionPeriod period = new SessionPeriod(LocalDate.of(2024, 1, 1), LocalDate.of(2024, 3, 31));
+
+        Session session = new Session(coverImage, period);
+
+        assertThat(session).isNotNull();
+        assertThat(session.getStatus()).isEqualTo(SessionStatus.PREPARING);
+    }
+}

From 35de848f4f3a5e70bdc679380b06af52fe947e7a Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 08:04:40 +0900
Subject: [PATCH 18/45] =?UTF-8?q?feat:=20=EB=AC=B4=EB=A3=8C/=EC=9C=A0?=
 =?UTF-8?q?=EB=A3=8C=20=EC=84=B8=EC=85=98=20=EB=8F=84=EB=A9=94=EC=9D=B8=20?=
 =?UTF-8?q?=EC=B6=94=EA=B0=80?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

FreeSession.java
- Session을 상속한 무료 세션 도메인 추가
- 별도 제약 없이 기본 생성자만 제공

PaidSession.java
- Session 확장하여 유료 세션 구현
- 최대 수강 인원(maxEnrollment) 및 수강료(fee) 보유
- maxEnrollment는 1명 이상이어야 하도록 검증 로직 추가

PaidSessionTest.java
- 정상 생성 테스트 추가
- 최대 수강 인원이 0명 이하일 경우 예외 발생 테스트 추가
---
 .../nextstep/courses/domain/FreeSession.java  |  7 +++++
 .../nextstep/courses/domain/PaidSession.java  | 19 ++++++++++++
 .../courses/domain/PaidSessionTest.java       | 31 +++++++++++++++++++
 3 files changed, 57 insertions(+)
 create mode 100644 src/main/java/nextstep/courses/domain/FreeSession.java
 create mode 100644 src/main/java/nextstep/courses/domain/PaidSession.java
 create mode 100644 src/test/java/nextstep/courses/domain/PaidSessionTest.java

diff --git a/src/main/java/nextstep/courses/domain/FreeSession.java b/src/main/java/nextstep/courses/domain/FreeSession.java
new file mode 100644
index 000000000..dfb9f4f90
--- /dev/null
+++ b/src/main/java/nextstep/courses/domain/FreeSession.java
@@ -0,0 +1,7 @@
+package nextstep.courses.domain;
+
+public class FreeSession extends Session {
+    public FreeSession(CoverImage coverImage, SessionPeriod period) {
+        super(coverImage, period);
+    }
+}
diff --git a/src/main/java/nextstep/courses/domain/PaidSession.java b/src/main/java/nextstep/courses/domain/PaidSession.java
new file mode 100644
index 000000000..0dc8aa870
--- /dev/null
+++ b/src/main/java/nextstep/courses/domain/PaidSession.java
@@ -0,0 +1,19 @@
+package nextstep.courses.domain;
+
+public class PaidSession extends Session {
+    private final int maxEnrollment;
+    private final Money fee;
+
+    public PaidSession(CoverImage coverImage, SessionPeriod period, int maxEnrollment, Money fee) {
+        super(coverImage, period);
+        validateMaxEnrollment(maxEnrollment);
+        this.maxEnrollment = maxEnrollment;
+        this.fee = fee;
+    }
+
+    private void validateMaxEnrollment(int maxEnrollment) {
+        if (maxEnrollment <= 0) {
+            throw new IllegalArgumentException(String.format("최대 수강 인원은 1명 이상이어야 합니다. (입력: %d)", maxEnrollment));
+        }
+    }
+}
diff --git a/src/test/java/nextstep/courses/domain/PaidSessionTest.java b/src/test/java/nextstep/courses/domain/PaidSessionTest.java
new file mode 100644
index 000000000..c8a8b343a
--- /dev/null
+++ b/src/test/java/nextstep/courses/domain/PaidSessionTest.java
@@ -0,0 +1,31 @@
+package nextstep.courses.domain;
+
+import static org.assertj.core.api.Assertions.*;
+
+import java.time.LocalDate;
+import org.junit.jupiter.api.DisplayNameGeneration;
+import org.junit.jupiter.api.DisplayNameGenerator;
+import org.junit.jupiter.api.Test;
+
+@DisplayNameGeneration(DisplayNameGenerator.ReplaceUnderscores.class)
+class PaidSessionTest {
+    @Test
+    void 생성자_정상입력_생성성공() {
+        CoverImage coverImage = new CoverImage("image.png", 1024, 300, 200);
+        SessionPeriod period = new SessionPeriod(LocalDate.of(2024, 1, 1), LocalDate.of(2024, 3, 31));
+        Money fee = new Money(50000);
+
+        assertThatCode(() -> new PaidSession(coverImage, period, 30, fee)).doesNotThrowAnyException();
+    }
+
+    @Test
+    void 생성자_최대인원0명_예외발생() {
+        CoverImage coverImage = new CoverImage("image.png", 1024, 300, 200);
+        SessionPeriod period = new SessionPeriod(LocalDate.of(2024, 1, 1), LocalDate.of(2024, 3, 31));
+        Money fee = new Money(50000);
+
+        assertThatThrownBy(() -> new PaidSession(coverImage, period, 0, fee))
+                .isInstanceOf(IllegalArgumentException.class)
+                .hasMessageContaining("최대 수강 인원은 1명 이상");
+    }
+}

From 1c5bcc93a8a2c5e19f41057d987179699da18486 Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 08:12:15 +0900
Subject: [PATCH 19/45] =?UTF-8?q?refactor:=20Session=EC=9D=84=20=EC=B6=94?=
 =?UTF-8?q?=EC=83=81=20=ED=81=B4=EB=9E=98=EC=8A=A4=EB=A1=9C=20=EC=A0=84?=
 =?UTF-8?q?=ED=99=98=ED=95=98=EA=B3=A0=20=ED=85=8C=EC=8A=A4=ED=8A=B8=20?=
 =?UTF-8?q?=EC=A0=95=EB=A6=AC?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Session.java
- Session 클래스를 abstract로 변경하여 FreeSession/PaidSession만 생성되도록 구조 개선

FreeSessionTest.java
- 기존 SessionTest를 FreeSessionTest로 변경
- FreeSession 생성 테스트로 수정
- 기본 상태가 PREPARING인지 검증

PaidSessionTest.java
- 정상 생성 테스트에서 객체 생성 후 기본 상태 PREPARING 검증하도록 수정
---
 src/main/java/nextstep/courses/domain/Session.java     |  2 +-
 .../domain/{SessionTest.java => FreeSessionTest.java}  | 10 ++++------
 .../java/nextstep/courses/domain/PaidSessionTest.java  |  5 ++++-
 3 files changed, 9 insertions(+), 8 deletions(-)
 rename src/test/java/nextstep/courses/domain/{SessionTest.java => FreeSessionTest.java} (60%)

diff --git a/src/main/java/nextstep/courses/domain/Session.java b/src/main/java/nextstep/courses/domain/Session.java
index b91974219..ce6a692f2 100644
--- a/src/main/java/nextstep/courses/domain/Session.java
+++ b/src/main/java/nextstep/courses/domain/Session.java
@@ -1,6 +1,6 @@
 package nextstep.courses.domain;
 
-public class Session {
+public abstract class Session {
     private Long id;
     private CoverImage coverImage;
     private SessionPeriod period;
diff --git a/src/test/java/nextstep/courses/domain/SessionTest.java b/src/test/java/nextstep/courses/domain/FreeSessionTest.java
similarity index 60%
rename from src/test/java/nextstep/courses/domain/SessionTest.java
rename to src/test/java/nextstep/courses/domain/FreeSessionTest.java
index a2fe7ef64..c43b675ae 100644
--- a/src/test/java/nextstep/courses/domain/SessionTest.java
+++ b/src/test/java/nextstep/courses/domain/FreeSessionTest.java
@@ -8,16 +8,14 @@
 import org.junit.jupiter.api.Test;
 
 @DisplayNameGeneration(DisplayNameGenerator.ReplaceUnderscores.class)
-class SessionTest {
+class FreeSessionTest {
 
     @Test
     void 생성자_정상입력_생성성공() {
-        CoverImage coverImage = new CoverImage("image.png", 1024, 300, 200);
-        SessionPeriod period = new SessionPeriod(LocalDate.of(2024, 1, 1), LocalDate.of(2024, 3, 31));
+        FreeSession session = new FreeSession(
+                new CoverImage("image.png", 1024, 300, 200),
+                new SessionPeriod(LocalDate.of(2024, 1, 1), LocalDate.of(2024, 3, 31)));
 
-        Session session = new Session(coverImage, period);
-
-        assertThat(session).isNotNull();
         assertThat(session.getStatus()).isEqualTo(SessionStatus.PREPARING);
     }
 }
diff --git a/src/test/java/nextstep/courses/domain/PaidSessionTest.java b/src/test/java/nextstep/courses/domain/PaidSessionTest.java
index c8a8b343a..4f2815c52 100644
--- a/src/test/java/nextstep/courses/domain/PaidSessionTest.java
+++ b/src/test/java/nextstep/courses/domain/PaidSessionTest.java
@@ -11,11 +11,14 @@
 class PaidSessionTest {
     @Test
     void 생성자_정상입력_생성성공() {
+        // given
         CoverImage coverImage = new CoverImage("image.png", 1024, 300, 200);
         SessionPeriod period = new SessionPeriod(LocalDate.of(2024, 1, 1), LocalDate.of(2024, 3, 31));
         Money fee = new Money(50000);
 
-        assertThatCode(() -> new PaidSession(coverImage, period, 30, fee)).doesNotThrowAnyException();
+        PaidSession session = new PaidSession(coverImage, period, 30, fee);
+
+        assertThat(session.getStatus()).isEqualTo(SessionStatus.PREPARING);
     }
 
     @Test

From 781867a22a5e6b1d58351dc818349d5bb92be324 Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 12:22:40 +0900
Subject: [PATCH 20/45] =?UTF-8?q?feat:=20=EC=88=98=EA=B0=95=EC=8B=A0?=
 =?UTF-8?q?=EC=B2=AD=20=EC=97=94=ED=8B=B0=ED=8B=B0=20=EB=B0=8F=20=EC=BB=AC?=
 =?UTF-8?q?=EB=A0=89=EC=85=98=20=EB=8F=84=EB=A9=94=EC=9D=B8=20=EC=B6=94?=
 =?UTF-8?q?=EA=B0=80?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Enrollment.java
- 수강신청 정보(id, studentId, createdAt)를 표현하는 엔티티 추가
- 기본 생성 시 id=0L로 초기화하는 생성자 제공

Enrollments.java
- Enrollment 리스트를 관리하는 도메인 컬렉션 추가
- 불변 리스트 복사 후 add 메서드로 수강신청 추가 기능 제공
---
 .../nextstep/courses/domain/Enrollment.java   | 19 ++++++++++++++++++
 .../nextstep/courses/domain/Enrollments.java  | 20 +++++++++++++++++++
 2 files changed, 39 insertions(+)
 create mode 100644 src/main/java/nextstep/courses/domain/Enrollment.java
 create mode 100644 src/main/java/nextstep/courses/domain/Enrollments.java

diff --git a/src/main/java/nextstep/courses/domain/Enrollment.java b/src/main/java/nextstep/courses/domain/Enrollment.java
new file mode 100644
index 000000000..a9b8c4a7d
--- /dev/null
+++ b/src/main/java/nextstep/courses/domain/Enrollment.java
@@ -0,0 +1,19 @@
+package nextstep.courses.domain;
+
+import java.time.LocalDateTime;
+
+public class Enrollment {
+    private Long id;
+    private Long studentId;
+    private LocalDateTime createdAt;
+
+    public Enrollment(Long studentId, LocalDateTime now) {
+        this(0L, studentId, now);
+    }
+
+    public Enrollment(Long id, Long studentId, LocalDateTime createdAt) {
+        this.id = id;
+        this.studentId = studentId;
+        this.createdAt = createdAt;
+    }
+}
diff --git a/src/main/java/nextstep/courses/domain/Enrollments.java b/src/main/java/nextstep/courses/domain/Enrollments.java
new file mode 100644
index 000000000..6b60f7b0c
--- /dev/null
+++ b/src/main/java/nextstep/courses/domain/Enrollments.java
@@ -0,0 +1,20 @@
+package nextstep.courses.domain;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class Enrollments {
+    private final List<Enrollment> enrollments;
+
+    public Enrollments() {
+        this(new ArrayList<>());
+    }
+
+    public Enrollments(List<Enrollment> enrollments) {
+        this.enrollments = new ArrayList<>(enrollments);
+    }
+
+    public void add(Enrollment enrollment) {
+        enrollments.add(enrollment);
+    }
+}

From c856a6004eb2649651ea4bcc08c313187b3a8e24 Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 12:36:10 +0900
Subject: [PATCH 21/45] =?UTF-8?q?feat:=20Session=EC=97=90=20=EC=88=98?=
 =?UTF-8?q?=EA=B0=95=EC=8B=A0=EC=B2=AD=20=EA=B8=B0=EB=8A=A5=20=EC=B6=94?=
 =?UTF-8?q?=EA=B0=80=20=EB=B0=8F=20Enrollment=EC=97=90=20sessionId=20?=
 =?UTF-8?q?=EB=B0=98=EC=98=81?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Enrollment.java
- sessionId 필드 추가
- 생성자에 sessionId 포함하도록 변경

Session.java
- Enrollments 컬렉션 필드 추가
- enroll(enrollment) 메서드 도입
- 모집 상태가 아닐 경우 예외 발생하도록 validateEnrollment 구현
- 기본 생성자는 빈 Enrollments로 초기화하도록 변경

SessionTest.java
- 기본 생성 시 상태가 PREPARING인지 검증
- 모집중이 아닐 때 enroll 호출 시 예외 발생 테스트 추가
---
 .../nextstep/courses/domain/Enrollment.java   |  8 ++--
 .../java/nextstep/courses/domain/Session.java | 18 +++++++--
 .../nextstep/courses/domain/SessionTest.java  | 39 +++++++++++++++++++
 3 files changed, 58 insertions(+), 7 deletions(-)
 create mode 100644 src/test/java/nextstep/courses/domain/SessionTest.java

diff --git a/src/main/java/nextstep/courses/domain/Enrollment.java b/src/main/java/nextstep/courses/domain/Enrollment.java
index a9b8c4a7d..91bee250e 100644
--- a/src/main/java/nextstep/courses/domain/Enrollment.java
+++ b/src/main/java/nextstep/courses/domain/Enrollment.java
@@ -4,15 +4,17 @@
 
 public class Enrollment {
     private Long id;
+    private Long sessionId;
     private Long studentId;
     private LocalDateTime createdAt;
 
-    public Enrollment(Long studentId, LocalDateTime now) {
-        this(0L, studentId, now);
+    public Enrollment(Long sessionId, Long studentId, LocalDateTime now) {
+        this(0L, sessionId, studentId, now);
     }
 
-    public Enrollment(Long id, Long studentId, LocalDateTime createdAt) {
+    public Enrollment(Long id, Long sessionId, Long studentId, LocalDateTime createdAt) {
         this.id = id;
+        this.sessionId = sessionId;
         this.studentId = studentId;
         this.createdAt = createdAt;
     }
diff --git a/src/main/java/nextstep/courses/domain/Session.java b/src/main/java/nextstep/courses/domain/Session.java
index ce6a692f2..8e95ff993 100644
--- a/src/main/java/nextstep/courses/domain/Session.java
+++ b/src/main/java/nextstep/courses/domain/Session.java
@@ -5,20 +5,30 @@ public abstract class Session {
     private CoverImage coverImage;
     private SessionPeriod period;
     private SessionStatus status;
+    private final Enrollments enrollments;
 
     public Session(CoverImage coverImage, SessionPeriod period) {
-        this(0L, coverImage, period, SessionStatus.PREPARING);
+        this(0L, coverImage, period, SessionStatus.PREPARING, new Enrollments());
     }
 
-    public Session(Long id, CoverImage coverImage, SessionPeriod period, SessionStatus status) {
+    public Session(
+            Long id, CoverImage coverImage, SessionPeriod period, SessionStatus status, Enrollments enrollments) {
         this.id = id;
         this.coverImage = coverImage;
         this.period = period;
         this.status = status;
+        this.enrollments = enrollments;
     }
 
-    public boolean canEnroll() {
-        return this.status.canEnroll();
+    public void enroll(Enrollment enrollment) {
+        validateEnrollment();
+        enrollments.add(enrollment);
+    }
+
+    protected void validateEnrollment() {
+        if (!status.canEnroll()) {
+            throw new IllegalStateException(String.format("모집중인 강의만 수강 신청이 가능합니다. (현재 상태: %s)", status));
+        }
     }
 
     public SessionStatus getStatus() {
diff --git a/src/test/java/nextstep/courses/domain/SessionTest.java b/src/test/java/nextstep/courses/domain/SessionTest.java
new file mode 100644
index 000000000..69ab8857d
--- /dev/null
+++ b/src/test/java/nextstep/courses/domain/SessionTest.java
@@ -0,0 +1,39 @@
+package nextstep.courses.domain;
+
+import static org.assertj.core.api.Assertions.*;
+
+import java.time.LocalDate;
+import java.time.LocalDateTime;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.DisplayNameGeneration;
+import org.junit.jupiter.api.DisplayNameGenerator;
+import org.junit.jupiter.api.Test;
+
+@DisplayNameGeneration(DisplayNameGenerator.ReplaceUnderscores.class)
+class SessionTest {
+    private CoverImage coverImage;
+    private SessionPeriod period;
+
+    @BeforeEach
+    void setUp() {
+        coverImage = new CoverImage("image.png", 1024, 300, 200);
+        period = new SessionPeriod(LocalDate.of(2024, 1, 1), LocalDate.of(2024, 3, 31));
+    }
+
+    @Test
+    void 생성자_정상입력_준비중상태() {
+        Session session = new FreeSession(coverImage, period);
+
+        assertThat(session.getStatus()).isEqualTo(SessionStatus.PREPARING);
+    }
+
+    @Test
+    void enroll_준비중_예외발생() {
+        Session session = new FreeSession(coverImage, period);
+        Enrollment enrollment = new Enrollment(1L, 1L, LocalDateTime.now());
+
+        assertThatThrownBy(() -> session.enroll(enrollment))
+                .isInstanceOf(IllegalStateException.class)
+                .hasMessageContaining("모집중인 강의만");
+    }
+}

From 4a4c9a3e6f257c6361dc03d8f66c3c7ea4dee092 Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 12:46:49 +0900
Subject: [PATCH 22/45] =?UTF-8?q?feat:=20=EC=84=B8=EC=85=98=20=EC=88=98?=
 =?UTF-8?q?=EA=B0=95=EC=8B=A0=EC=B2=AD=20=EA=B8=B0=EB=8A=A5=20=ED=99=95?=
 =?UTF-8?q?=EC=9E=A5=20=EB=B0=8F=20FreeSession=20=EC=83=9D=EC=84=B1?=
 =?UTF-8?q?=EC=9E=90=20=EC=B6=94=EA=B0=80?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Enrollments.java
- 내부 리스트명을 values로 변경
- count() 메서드 추가로 총 신청 인원 조회 가능

FreeSession.java
- 상태를 지정해 생성할 수 있는 생성자 추가

Session.java
- 상태 지정 생성자 추가
- enrollmentCount()로 신청 인원 조회 기능 제공
- enroll 시 모집중 상태가 아니면 예외 발생하도록 유지

SessionTest.java
- 모집중(enrolling)일 때 수강신청 성공 테스트 추가
- PREPARING/CLOSED 상태에서 예외 발생하는지 파라미터화 테스트로 검증
---
 .../nextstep/courses/domain/Enrollments.java  | 12 ++++++++----
 .../nextstep/courses/domain/FreeSession.java  |  4 ++++
 .../java/nextstep/courses/domain/Session.java |  8 ++++++++
 .../nextstep/courses/domain/SessionTest.java  | 19 +++++++++++++++++--
 4 files changed, 37 insertions(+), 6 deletions(-)

diff --git a/src/main/java/nextstep/courses/domain/Enrollments.java b/src/main/java/nextstep/courses/domain/Enrollments.java
index 6b60f7b0c..ebb07909c 100644
--- a/src/main/java/nextstep/courses/domain/Enrollments.java
+++ b/src/main/java/nextstep/courses/domain/Enrollments.java
@@ -4,17 +4,21 @@
 import java.util.List;
 
 public class Enrollments {
-    private final List<Enrollment> enrollments;
+    private final List<Enrollment> values;
 
     public Enrollments() {
         this(new ArrayList<>());
     }
 
-    public Enrollments(List<Enrollment> enrollments) {
-        this.enrollments = new ArrayList<>(enrollments);
+    public Enrollments(List<Enrollment> values) {
+        this.values = new ArrayList<>(values);
     }
 
     public void add(Enrollment enrollment) {
-        enrollments.add(enrollment);
+        this.values.add(enrollment);
+    }
+
+    public int count() {
+        return this.values.size();
     }
 }
diff --git a/src/main/java/nextstep/courses/domain/FreeSession.java b/src/main/java/nextstep/courses/domain/FreeSession.java
index dfb9f4f90..283d2c219 100644
--- a/src/main/java/nextstep/courses/domain/FreeSession.java
+++ b/src/main/java/nextstep/courses/domain/FreeSession.java
@@ -4,4 +4,8 @@ public class FreeSession extends Session {
     public FreeSession(CoverImage coverImage, SessionPeriod period) {
         super(coverImage, period);
     }
+
+    public FreeSession(CoverImage coverImage, SessionPeriod period, SessionStatus status) {
+        super(coverImage, period, status);
+    }
 }
diff --git a/src/main/java/nextstep/courses/domain/Session.java b/src/main/java/nextstep/courses/domain/Session.java
index 8e95ff993..a2ead1af4 100644
--- a/src/main/java/nextstep/courses/domain/Session.java
+++ b/src/main/java/nextstep/courses/domain/Session.java
@@ -11,6 +11,10 @@ public Session(CoverImage coverImage, SessionPeriod period) {
         this(0L, coverImage, period, SessionStatus.PREPARING, new Enrollments());
     }
 
+    public Session(CoverImage coverImage, SessionPeriod period, SessionStatus status) {
+        this(0L, coverImage, period, status, new Enrollments());
+    }
+
     public Session(
             Long id, CoverImage coverImage, SessionPeriod period, SessionStatus status, Enrollments enrollments) {
         this.id = id;
@@ -31,6 +35,10 @@ protected void validateEnrollment() {
         }
     }
 
+    public int enrollmentCount() {
+        return enrollments.count();
+    }
+
     public SessionStatus getStatus() {
         return this.status;
     }
diff --git a/src/test/java/nextstep/courses/domain/SessionTest.java b/src/test/java/nextstep/courses/domain/SessionTest.java
index 69ab8857d..5dabf0870 100644
--- a/src/test/java/nextstep/courses/domain/SessionTest.java
+++ b/src/test/java/nextstep/courses/domain/SessionTest.java
@@ -8,6 +8,8 @@
 import org.junit.jupiter.api.DisplayNameGeneration;
 import org.junit.jupiter.api.DisplayNameGenerator;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.EnumSource;
 
 @DisplayNameGeneration(DisplayNameGenerator.ReplaceUnderscores.class)
 class SessionTest {
@@ -28,8 +30,21 @@ void setUp() {
     }
 
     @Test
-    void enroll_준비중_예외발생() {
-        Session session = new FreeSession(coverImage, period);
+    void enroll_모집중_성공() {
+        Session session = new FreeSession(coverImage, period, SessionStatus.RECRUITING);
+        Enrollment enrollment = new Enrollment(1L, 1L, LocalDateTime.now());
+
+        session.enroll(enrollment);
+
+        assertThat(session.enrollmentCount()).isEqualTo(1);
+    }
+
+    @ParameterizedTest(name = "상태:{0}")
+    @EnumSource(
+            value = SessionStatus.class,
+            names = {"PREPARING", "CLOSED"})
+    void enroll_모집중이아닐시_예외발생(SessionStatus status) {
+        Session session = new FreeSession(coverImage, period, status);
         Enrollment enrollment = new Enrollment(1L, 1L, LocalDateTime.now());
 
         assertThatThrownBy(() -> session.enroll(enrollment))

From bd668f30974dd48c2ec03c369ab8d4e9ea7dae5f Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 13:06:25 +0900
Subject: [PATCH 23/45] =?UTF-8?q?feat:=20=EC=9C=A0=EB=A3=8C=20=EC=84=B8?=
 =?UTF-8?q?=EC=85=98=20=EA=B2=B0=EC=A0=9C=20=EA=B2=80=EC=A6=9D=20=EB=B0=8F?=
 =?UTF-8?q?=20=EC=83=81=ED=83=9C=20=EA=B2=80=EC=A6=9D=20=EB=A1=9C=EC=A7=81?=
 =?UTF-8?q?=20=EA=B0=95=ED=99=94?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

PaidSession.java
- 상태 지정 생성자 추가
- enroll(enrollment, payment) 메서드로 결제 금액 일치 여부 검증 후 부모 enroll 호출
- 결제 불일치 시 예외 발생하도록 validatePayment 추가

Session.java
- enroll 시 상태 검증 메서드명을 validateStatus로 변경하여 의미 명확화

FreeSessionTest.java
- FreeSession 정상 생성 테스트 명확화

PaidSessionTest.java
- 공통 객체 setUp으로 정리
- 정상 enroll 테스트 추가
- 결제 금액 불일치 시 예외 발생 테스트 추가
---
 .../nextstep/courses/domain/PaidSession.java  | 18 ++++++++
 .../java/nextstep/courses/domain/Session.java |  4 +-
 .../courses/domain/FreeSessionTest.java       |  7 ++-
 .../courses/domain/PaidSessionTest.java       | 45 +++++++++++++++----
 4 files changed, 60 insertions(+), 14 deletions(-)

diff --git a/src/main/java/nextstep/courses/domain/PaidSession.java b/src/main/java/nextstep/courses/domain/PaidSession.java
index 0dc8aa870..49d5b391e 100644
--- a/src/main/java/nextstep/courses/domain/PaidSession.java
+++ b/src/main/java/nextstep/courses/domain/PaidSession.java
@@ -11,9 +11,27 @@ public PaidSession(CoverImage coverImage, SessionPeriod period, int maxEnrollmen
         this.fee = fee;
     }
 
+    public PaidSession(
+            CoverImage coverImage, SessionPeriod period, SessionStatus status, int maxEnrollment, Money fee) {
+        super(coverImage, period, status);
+        this.maxEnrollment = maxEnrollment;
+        this.fee = fee;
+    }
+
     private void validateMaxEnrollment(int maxEnrollment) {
         if (maxEnrollment <= 0) {
             throw new IllegalArgumentException(String.format("최대 수강 인원은 1명 이상이어야 합니다. (입력: %d)", maxEnrollment));
         }
     }
+
+    public void enroll(Enrollment enrollment, Money payment) {
+        validatePayment(payment);
+        super.enroll(enrollment);
+    }
+
+    private void validatePayment(Money payment) {
+        if (!fee.isSameAs(payment)) {
+            throw new IllegalArgumentException("결제 금액이 수강료와 일치하지 않습니다.");
+        }
+    }
 }
diff --git a/src/main/java/nextstep/courses/domain/Session.java b/src/main/java/nextstep/courses/domain/Session.java
index a2ead1af4..6c8eb8a6a 100644
--- a/src/main/java/nextstep/courses/domain/Session.java
+++ b/src/main/java/nextstep/courses/domain/Session.java
@@ -25,11 +25,11 @@ public Session(
     }
 
     public void enroll(Enrollment enrollment) {
-        validateEnrollment();
+        validateStatus();
         enrollments.add(enrollment);
     }
 
-    protected void validateEnrollment() {
+    protected void validateStatus() {
         if (!status.canEnroll()) {
             throw new IllegalStateException(String.format("모집중인 강의만 수강 신청이 가능합니다. (현재 상태: %s)", status));
         }
diff --git a/src/test/java/nextstep/courses/domain/FreeSessionTest.java b/src/test/java/nextstep/courses/domain/FreeSessionTest.java
index c43b675ae..e9751f43f 100644
--- a/src/test/java/nextstep/courses/domain/FreeSessionTest.java
+++ b/src/test/java/nextstep/courses/domain/FreeSessionTest.java
@@ -12,10 +12,9 @@ class FreeSessionTest {
 
     @Test
     void 생성자_정상입력_생성성공() {
-        FreeSession session = new FreeSession(
-                new CoverImage("image.png", 1024, 300, 200),
-                new SessionPeriod(LocalDate.of(2024, 1, 1), LocalDate.of(2024, 3, 31)));
+        CoverImage coverImage = new CoverImage("image.png", 1024, 300, 200);
+        SessionPeriod sessionPeriod = new SessionPeriod(LocalDate.of(2024, 1, 1), LocalDate.of(2024, 3, 31));
 
-        assertThat(session.getStatus()).isEqualTo(SessionStatus.PREPARING);
+        assertThatCode(() -> new FreeSession(coverImage, sessionPeriod)).doesNotThrowAnyException();
     }
 }
diff --git a/src/test/java/nextstep/courses/domain/PaidSessionTest.java b/src/test/java/nextstep/courses/domain/PaidSessionTest.java
index 4f2815c52..b94809ab9 100644
--- a/src/test/java/nextstep/courses/domain/PaidSessionTest.java
+++ b/src/test/java/nextstep/courses/domain/PaidSessionTest.java
@@ -3,22 +3,29 @@
 import static org.assertj.core.api.Assertions.*;
 
 import java.time.LocalDate;
+import java.time.LocalDateTime;
+import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.DisplayNameGeneration;
 import org.junit.jupiter.api.DisplayNameGenerator;
 import org.junit.jupiter.api.Test;
 
 @DisplayNameGeneration(DisplayNameGenerator.ReplaceUnderscores.class)
 class PaidSessionTest {
-    @Test
-    void 생성자_정상입력_생성성공() {
-        // given
-        CoverImage coverImage = new CoverImage("image.png", 1024, 300, 200);
-        SessionPeriod period = new SessionPeriod(LocalDate.of(2024, 1, 1), LocalDate.of(2024, 3, 31));
-        Money fee = new Money(50000);
 
-        PaidSession session = new PaidSession(coverImage, period, 30, fee);
+    private CoverImage coverImage;
+    private SessionPeriod period;
+    private Money fee;
 
-        assertThat(session.getStatus()).isEqualTo(SessionStatus.PREPARING);
+    @BeforeEach
+    void setUp() {
+        coverImage = new CoverImage("image.png", 1024, 300, 200);
+        period = new SessionPeriod(LocalDate.of(2024, 1, 1), LocalDate.of(2024, 3, 31));
+        fee = new Money(50000);
+    }
+
+    @Test
+    void 생성자_정상입력_생성성공() {
+        assertThatCode(() -> new PaidSession(coverImage, period, 30, fee)).doesNotThrowAnyException();
     }
 
     @Test
@@ -31,4 +38,26 @@ class PaidSessionTest {
                 .isInstanceOf(IllegalArgumentException.class)
                 .hasMessageContaining("최대 수강 인원은 1명 이상");
     }
+
+    @Test
+    void enroll_정상입력_성공() {
+        PaidSession session = new PaidSession(coverImage, period, SessionStatus.RECRUITING, 3, fee);
+        Enrollment enrollment = new Enrollment(1L, 1L, LocalDateTime.now());
+        Money payment = new Money(50000);
+
+        session.enroll(enrollment, payment);
+
+        assertThat(session.enrollmentCount()).isEqualTo(1);
+    }
+
+    @Test
+    void enroll_결제금액불일치_예외발생() {
+        PaidSession session = new PaidSession(coverImage, period, SessionStatus.RECRUITING, 3, fee);
+        Enrollment enrollment = new Enrollment(1L, 1L, LocalDateTime.now());
+        Money wrongPayment = new Money(30000);
+
+        assertThatThrownBy(() -> session.enroll(enrollment, wrongPayment))
+                .isInstanceOf(IllegalArgumentException.class)
+                .hasMessageContaining("결제 금액이 수강료와 일치하지 않습니다");
+    }
 }

From 50f0f02c1f0cb88ab7f19658c49414dd9c7d88b6 Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 13:09:41 +0900
Subject: [PATCH 24/45] =?UTF-8?q?feat:=20PaidSession=20=EC=88=98=EA=B0=95?=
 =?UTF-8?q?=20=EC=9D=B8=EC=9B=90=20=EC=A0=9C=ED=95=9C=20=EA=B2=80=EC=A6=9D?=
 =?UTF-8?q?=20=EC=B6=94=EA=B0=80?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

PaidSession.java
- enroll 시 결제 검증 후 정원 초과 여부 validateCapacity 추가
- 정원 도달 시 IllegalStateException 발생

PaidSessionTest.java
- 최대 정원 초과 시 예외 발생 테스트 추가
---
 .../java/nextstep/courses/domain/PaidSession.java   |  7 +++++++
 .../nextstep/courses/domain/PaidSessionTest.java    | 13 +++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/src/main/java/nextstep/courses/domain/PaidSession.java b/src/main/java/nextstep/courses/domain/PaidSession.java
index 49d5b391e..6afd83e0a 100644
--- a/src/main/java/nextstep/courses/domain/PaidSession.java
+++ b/src/main/java/nextstep/courses/domain/PaidSession.java
@@ -26,6 +26,7 @@ private void validateMaxEnrollment(int maxEnrollment) {
 
     public void enroll(Enrollment enrollment, Money payment) {
         validatePayment(payment);
+        validateCapacity();
         super.enroll(enrollment);
     }
 
@@ -34,4 +35,10 @@ private void validatePayment(Money payment) {
             throw new IllegalArgumentException("결제 금액이 수강료와 일치하지 않습니다.");
         }
     }
+
+    private void validateCapacity() {
+        if (enrollmentCount() >= maxEnrollment) {
+            throw new IllegalStateException(String.format("수강 인원이 초과되었습니다. (최대: %d명)", maxEnrollment));
+        }
+    }
 }
diff --git a/src/test/java/nextstep/courses/domain/PaidSessionTest.java b/src/test/java/nextstep/courses/domain/PaidSessionTest.java
index b94809ab9..9cfbc6471 100644
--- a/src/test/java/nextstep/courses/domain/PaidSessionTest.java
+++ b/src/test/java/nextstep/courses/domain/PaidSessionTest.java
@@ -60,4 +60,17 @@ void setUp() {
                 .isInstanceOf(IllegalArgumentException.class)
                 .hasMessageContaining("결제 금액이 수강료와 일치하지 않습니다");
     }
+
+    @Test
+    void enroll_인원초과_예외발생() {
+        PaidSession session = new PaidSession(coverImage, period, SessionStatus.RECRUITING, 2, fee);
+        Money payment = new Money(50000);
+
+        session.enroll(new Enrollment(1L, 1L, LocalDateTime.now()), payment);
+        session.enroll(new Enrollment(2L, 2L, LocalDateTime.now()), payment);
+
+        assertThatThrownBy(() -> session.enroll(new Enrollment(3L, 3L, LocalDateTime.now()), payment))
+                .isInstanceOf(IllegalStateException.class)
+                .hasMessageContaining("수강 인원이 초과");
+    }
 }

From a7b32e6594371bc1c63b4e8b5826807cd1618ccb Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 20:15:43 +0900
Subject: [PATCH 25/45] =?UTF-8?q?refactor:=20Course=EC=97=90=EC=84=9C=20ge?=
 =?UTF-8?q?neration=20=EC=A0=9C=EA=B1=B0=20=EB=B0=8F=20=EA=B4=80=EB=A0=A8?=
 =?UTF-8?q?=20=EC=BD=94=EB=93=9C=20=EC=A0=95=EB=A6=AC?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Course.java
- generation 필드 제거
- generation을 받던 생성자 삭제 및 기존 생성자 시그니처 정리
- findById 매핑 로직에서 generation 관련 코드 제거

JdbcCourseRepository.java
- insert 쿼리에서 generation 제거
- select 쿼리 컬럼 목록에서 generation 제거
- RowMapper 매핑 인덱스 수정

schema.sql
- course 테이블에서 generation 컬럼 삭제

CourseTest.java
- 생성자 변경에 맞게 테스트 파라미터 수정

CourseRepositoryTest.java
- generation 비교 제거
- 변경된 생성자 사용하도록 수정
---
 .../java/nextstep/courses/domain/Course.java   | 18 +++++-------------
 .../infrastructure/JdbcCourseRepository.java   | 14 ++++++--------
 src/main/resources/schema.sql                  |  1 -
 .../nextstep/courses/domain/CourseTest.java    |  2 +-
 .../infrastructure/CourseRepositoryTest.java   |  3 +--
 5 files changed, 13 insertions(+), 25 deletions(-)

diff --git a/src/main/java/nextstep/courses/domain/Course.java b/src/main/java/nextstep/courses/domain/Course.java
index 97e5b383c..96a2b65ca 100644
--- a/src/main/java/nextstep/courses/domain/Course.java
+++ b/src/main/java/nextstep/courses/domain/Course.java
@@ -7,8 +7,6 @@ public class Course {
 
     private String title;
 
-    private int generation;
-
     private Long creatorId;
 
     private LocalDateTime createdAt;
@@ -17,19 +15,17 @@ public class Course {
 
     public Course() {}
 
-    public Course(String title, int generation, Long creatorId, LocalDateTime now) {
-        this(0L, title, generation, creatorId, now, null);
+    public Course(String title, Long creatorId, LocalDateTime now) {
+        this(0L, title, creatorId, now, null);
     }
 
-    public Course(String title, int generation, Long creatorId) {
-        this(0L, title, generation, creatorId, LocalDateTime.now(), null);
+    public Course(String title, Long creatorId) {
+        this(0L, title, creatorId, LocalDateTime.now(), null);
     }
 
-    public Course(
-            Long id, String title, int generation, Long creatorId, LocalDateTime createdAt, LocalDateTime updatedAt) {
+    public Course(Long id, String title, Long creatorId, LocalDateTime createdAt, LocalDateTime updatedAt) {
         this.id = id;
         this.title = title;
-        this.generation = generation;
         this.creatorId = creatorId;
         this.createdAt = createdAt;
         this.updatedAt = updatedAt;
@@ -43,10 +39,6 @@ public Long getCreatorId() {
         return creatorId;
     }
 
-    public int getGeneration() {
-        return generation;
-    }
-
     public LocalDateTime getCreatedAt() {
         return createdAt;
     }
diff --git a/src/main/java/nextstep/courses/infrastructure/JdbcCourseRepository.java b/src/main/java/nextstep/courses/infrastructure/JdbcCourseRepository.java
index 3f21435f7..475bf9a6f 100644
--- a/src/main/java/nextstep/courses/infrastructure/JdbcCourseRepository.java
+++ b/src/main/java/nextstep/courses/infrastructure/JdbcCourseRepository.java
@@ -18,21 +18,19 @@ public JdbcCourseRepository(JdbcOperations jdbcTemplate) {
 
     @Override
     public int save(Course course) {
-        String sql = "insert into course (title, generation, creator_id, created_at) values(?, ?, ?, ?)";
-        return jdbcTemplate.update(
-                sql, course.getTitle(), course.getGeneration(), course.getCreatorId(), course.getCreatedAt());
+        String sql = "insert into course (title, creator_id, created_at) values(?, ?, ?)";
+        return jdbcTemplate.update(sql, course.getTitle(), course.getCreatorId(), course.getCreatedAt());
     }
 
     @Override
     public Course findById(Long id) {
-        String sql = "select id, title, generation, creator_id, created_at, updated_at from course where id = ?";
+        String sql = "select id, title,creator_id, created_at, updated_at from course where id = ?";
         RowMapper<Course> rowMapper = (rs, rowNum) -> new Course(
                 rs.getLong(1),
                 rs.getString(2),
-                rs.getInt(3),
-                rs.getLong(4),
-                toLocalDateTime(rs.getTimestamp(5)),
-                toLocalDateTime(rs.getTimestamp(6)));
+                rs.getLong(3),
+                toLocalDateTime(rs.getTimestamp(4)),
+                toLocalDateTime(rs.getTimestamp(5)));
         return jdbcTemplate.queryForObject(sql, rowMapper, id);
     }
 
diff --git a/src/main/resources/schema.sql b/src/main/resources/schema.sql
index 746fcb244..8d5a988c8 100644
--- a/src/main/resources/schema.sql
+++ b/src/main/resources/schema.sql
@@ -1,7 +1,6 @@
 create table course (
     id bigint generated by default as identity,
     title varchar(255) not null,
-    generation INT NOT NULL,
     creator_id bigint not null,
     created_at timestamp not null,
     updated_at timestamp,
diff --git a/src/test/java/nextstep/courses/domain/CourseTest.java b/src/test/java/nextstep/courses/domain/CourseTest.java
index 58e5bd30d..6ab085660 100644
--- a/src/test/java/nextstep/courses/domain/CourseTest.java
+++ b/src/test/java/nextstep/courses/domain/CourseTest.java
@@ -13,6 +13,6 @@ class CourseTest {
     @Test
     void 생성자_정상입력_생성성공() {
         LocalDateTime fixedNow = LocalDateTime.now();
-        assertThatCode(() -> new Course("과정명", 1, 1L, fixedNow)).doesNotThrowAnyException();
+        assertThatCode(() -> new Course("과정명", 1L, fixedNow)).doesNotThrowAnyException();
     }
 }
diff --git a/src/test/java/nextstep/courses/infrastructure/CourseRepositoryTest.java b/src/test/java/nextstep/courses/infrastructure/CourseRepositoryTest.java
index c79525793..e30a074e4 100644
--- a/src/test/java/nextstep/courses/infrastructure/CourseRepositoryTest.java
+++ b/src/test/java/nextstep/courses/infrastructure/CourseRepositoryTest.java
@@ -30,12 +30,11 @@ void setUp() {
     @Test
     void crud() {
         LocalDateTime fixednow = LocalDateTime.now();
-        Course course = new Course("TDD, 클린 코드 with Java", 1, 1L, fixednow);
+        Course course = new Course("TDD, 클린 코드 with Java", 1L, fixednow);
         int count = courseRepository.save(course);
         assertThat(count).isEqualTo(1);
         Course savedCourse = courseRepository.findById(1L);
         assertThat(course.getTitle()).isEqualTo(savedCourse.getTitle());
-        assertThat(course.getGeneration()).isEqualTo(savedCourse.getGeneration());
         assertThat(course.getCreatorId()).isEqualTo(savedCourse.getCreatorId());
         assertThat(course.getCreatedAt()).isEqualTo(savedCourse.getCreatedAt());
         LOGGER.debug("Course: {}", savedCourse);

From d3803a6941f9bd1341dd9933811dbd23f18cacc4 Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 20:23:18 +0900
Subject: [PATCH 26/45] =?UTF-8?q?feat:=20Course=EC=97=90=20Sessions=20?=
 =?UTF-8?q?=EC=B6=94=EA=B0=80=20=EB=B0=8F=20=EC=83=9D=EC=84=B1=EC=9E=90/?=
 =?UTF-8?q?=EB=A7=A4=ED=95=91=20=EA=B5=AC=EC=A1=B0=20=ED=99=95=EC=9E=A5?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Course.java
- Sessions 컬렉션 필드 추가
- 기본 생성자 제거 및 sessions 초기화 포함한 생성자 구조로 변경
- 신규 생성자에서 Sessions를 주입받도록 확장
- 기존 필드 초기화 로직 정리

Sessions.java
- Session 리스트를 보관하는 컬렉션 VO 추가
- add(), count() 기능 제공
- 기본 생성 시 빈 리스트로 초기화

JdbcCourseRepository.java
- RowMapper에서 sessions는 아직 영속화 대상이 아니므로 null로 매핑 처리
---
 .../java/nextstep/courses/domain/Course.java  | 19 ++++++++-------
 .../nextstep/courses/domain/Sessions.java     | 24 +++++++++++++++++++
 .../infrastructure/JdbcCourseRepository.java  |  1 +
 3 files changed, 36 insertions(+), 8 deletions(-)
 create mode 100644 src/main/java/nextstep/courses/domain/Sessions.java

diff --git a/src/main/java/nextstep/courses/domain/Course.java b/src/main/java/nextstep/courses/domain/Course.java
index 96a2b65ca..e94346175 100644
--- a/src/main/java/nextstep/courses/domain/Course.java
+++ b/src/main/java/nextstep/courses/domain/Course.java
@@ -9,24 +9,27 @@ public class Course {
 
     private Long creatorId;
 
+    private final Sessions sessions;
+
     private LocalDateTime createdAt;
 
     private LocalDateTime updatedAt;
 
-    public Course() {}
-
     public Course(String title, Long creatorId, LocalDateTime now) {
-        this(0L, title, creatorId, now, null);
-    }
-
-    public Course(String title, Long creatorId) {
-        this(0L, title, creatorId, LocalDateTime.now(), null);
+        this(0L, title, creatorId, new Sessions(), now, null);
     }
 
-    public Course(Long id, String title, Long creatorId, LocalDateTime createdAt, LocalDateTime updatedAt) {
+    public Course(
+            Long id,
+            String title,
+            Long creatorId,
+            Sessions sessions,
+            LocalDateTime createdAt,
+            LocalDateTime updatedAt) {
         this.id = id;
         this.title = title;
         this.creatorId = creatorId;
+        this.sessions = sessions;
         this.createdAt = createdAt;
         this.updatedAt = updatedAt;
     }
diff --git a/src/main/java/nextstep/courses/domain/Sessions.java b/src/main/java/nextstep/courses/domain/Sessions.java
new file mode 100644
index 000000000..dfd1d6536
--- /dev/null
+++ b/src/main/java/nextstep/courses/domain/Sessions.java
@@ -0,0 +1,24 @@
+package nextstep.courses.domain;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class Sessions {
+    private final List<Session> values;
+
+    public Sessions() {
+        this(new ArrayList<>());
+    }
+
+    public Sessions(List<Session> values) {
+        this.values = values;
+    }
+
+    public void add(Session session) {
+        this.values.add(session);
+    }
+
+    public int count() {
+        return this.values.size();
+    }
+}
diff --git a/src/main/java/nextstep/courses/infrastructure/JdbcCourseRepository.java b/src/main/java/nextstep/courses/infrastructure/JdbcCourseRepository.java
index 475bf9a6f..663695b18 100644
--- a/src/main/java/nextstep/courses/infrastructure/JdbcCourseRepository.java
+++ b/src/main/java/nextstep/courses/infrastructure/JdbcCourseRepository.java
@@ -29,6 +29,7 @@ public Course findById(Long id) {
                 rs.getLong(1),
                 rs.getString(2),
                 rs.getLong(3),
+                null,
                 toLocalDateTime(rs.getTimestamp(4)),
                 toLocalDateTime(rs.getTimestamp(5)));
         return jdbcTemplate.queryForObject(sql, rowMapper, id);

From ea535b88d778c07c4663ffa6dbab14a34692dbfc Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 20:45:08 +0900
Subject: [PATCH 27/45] =?UTF-8?q?feat:=20Course=EC=97=90=20Session=20?=
 =?UTF-8?q?=EA=B4=80=EB=A6=AC=20=EA=B8=B0=EB=8A=A5=20=EC=B6=94=EA=B0=80=20?=
 =?UTF-8?q?=EB=B0=8F=20=EC=84=B8=EC=85=98=20=EC=BB=AC=EB=A0=89=EC=85=98=20?=
 =?UTF-8?q?=EC=95=88=EC=A0=95=ED=99=94?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Course.java
- addSession() 메서드 추가로 코스에 세션 등록 기능 제공
- sessionCount() 메서드로 세션 수 조회 기능 추가

PaidSession.java
- 상태 지정 생성자에서 maxEnrollment 유효성 검증 누락 문제를 수정하여 validateMaxEnrollment 호출 추가

Sessions.java
- 내부 리스트를 방어적 복사(new ArrayList<>(values))로 초기화해 불변성 강화
---
 src/main/java/nextstep/courses/domain/Course.java      | 8 ++++++++
 src/main/java/nextstep/courses/domain/PaidSession.java | 1 +
 src/main/java/nextstep/courses/domain/Sessions.java    | 2 +-
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/main/java/nextstep/courses/domain/Course.java b/src/main/java/nextstep/courses/domain/Course.java
index e94346175..f3083f9e3 100644
--- a/src/main/java/nextstep/courses/domain/Course.java
+++ b/src/main/java/nextstep/courses/domain/Course.java
@@ -34,6 +34,14 @@ public Course(
         this.updatedAt = updatedAt;
     }
 
+    public void addSession(Session session) {
+        sessions.add(session);
+    }
+
+    public int sessionCount() {
+        return sessions.count();
+    }
+
     public String getTitle() {
         return title;
     }
diff --git a/src/main/java/nextstep/courses/domain/PaidSession.java b/src/main/java/nextstep/courses/domain/PaidSession.java
index 6afd83e0a..b7fe1bcb2 100644
--- a/src/main/java/nextstep/courses/domain/PaidSession.java
+++ b/src/main/java/nextstep/courses/domain/PaidSession.java
@@ -14,6 +14,7 @@ public PaidSession(CoverImage coverImage, SessionPeriod period, int maxEnrollmen
     public PaidSession(
             CoverImage coverImage, SessionPeriod period, SessionStatus status, int maxEnrollment, Money fee) {
         super(coverImage, period, status);
+        validateMaxEnrollment(maxEnrollment);
         this.maxEnrollment = maxEnrollment;
         this.fee = fee;
     }
diff --git a/src/main/java/nextstep/courses/domain/Sessions.java b/src/main/java/nextstep/courses/domain/Sessions.java
index dfd1d6536..5e5d6a1aa 100644
--- a/src/main/java/nextstep/courses/domain/Sessions.java
+++ b/src/main/java/nextstep/courses/domain/Sessions.java
@@ -11,7 +11,7 @@ public Sessions() {
     }
 
     public Sessions(List<Session> values) {
-        this.values = values;
+        this.values = new ArrayList<>(values);
     }
 
     public void add(Session session) {

From 79a4ccb2e9959ff010a87851077e5067b9c0b668 Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 20:50:38 +0900
Subject: [PATCH 28/45] =?UTF-8?q?refactor:=20PaidSession=20=ED=95=84?=
 =?UTF-8?q?=EB=93=9C=EB=AA=85=20=EC=9D=98=EB=AF=B8=20=EB=AA=85=ED=99=95?=
 =?UTF-8?q?=ED=99=94=20=EB=B0=8F=20=EC=9A=A9=EC=96=B4=20=EC=9D=BC=EA=B4=80?=
 =?UTF-8?q?=EC=84=B1=20=EA=B0=9C=EC=84=A0?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

PaidSession.java
- maxEnrollment → capacity로 필드명 변경
- fee → price로 필드명 변경
- 생성자 파라미터 및 필드 초기화 로직을 새로운 용어에 맞게 수정
- 결제 검증 로직에서 fee → price로 업데이트
- 정원 검증 로직에서 maxEnrollment → capacity로 일관성 유지
---
 .../nextstep/courses/domain/PaidSession.java  | 27 +++++++++----------
 1 file changed, 13 insertions(+), 14 deletions(-)

diff --git a/src/main/java/nextstep/courses/domain/PaidSession.java b/src/main/java/nextstep/courses/domain/PaidSession.java
index b7fe1bcb2..e9f2400d7 100644
--- a/src/main/java/nextstep/courses/domain/PaidSession.java
+++ b/src/main/java/nextstep/courses/domain/PaidSession.java
@@ -1,22 +1,21 @@
 package nextstep.courses.domain;
 
 public class PaidSession extends Session {
-    private final int maxEnrollment;
-    private final Money fee;
+    private final int capacity;
+    private final Money price;
 
-    public PaidSession(CoverImage coverImage, SessionPeriod period, int maxEnrollment, Money fee) {
+    public PaidSession(CoverImage coverImage, SessionPeriod period, int capacity, Money price) {
         super(coverImage, period);
-        validateMaxEnrollment(maxEnrollment);
-        this.maxEnrollment = maxEnrollment;
-        this.fee = fee;
+        validateMaxEnrollment(capacity);
+        this.capacity = capacity;
+        this.price = price;
     }
 
-    public PaidSession(
-            CoverImage coverImage, SessionPeriod period, SessionStatus status, int maxEnrollment, Money fee) {
+    public PaidSession(CoverImage coverImage, SessionPeriod period, SessionStatus status, int capacity, Money price) {
         super(coverImage, period, status);
-        validateMaxEnrollment(maxEnrollment);
-        this.maxEnrollment = maxEnrollment;
-        this.fee = fee;
+        validateMaxEnrollment(capacity);
+        this.capacity = capacity;
+        this.price = price;
     }
 
     private void validateMaxEnrollment(int maxEnrollment) {
@@ -32,14 +31,14 @@ public void enroll(Enrollment enrollment, Money payment) {
     }
 
     private void validatePayment(Money payment) {
-        if (!fee.isSameAs(payment)) {
+        if (!price.isSameAs(payment)) {
             throw new IllegalArgumentException("결제 금액이 수강료와 일치하지 않습니다.");
         }
     }
 
     private void validateCapacity() {
-        if (enrollmentCount() >= maxEnrollment) {
-            throw new IllegalStateException(String.format("수강 인원이 초과되었습니다. (최대: %d명)", maxEnrollment));
+        if (enrollmentCount() >= capacity) {
+            throw new IllegalStateException(String.format("수강 인원이 초과되었습니다. (최대: %d명)", capacity));
         }
     }
 }

From d8cc1b81674e090c5972fc49b8fc63a6bd03bcb5 Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 20:55:35 +0900
Subject: [PATCH 29/45] =?UTF-8?q?feat:=20=EC=88=98=EA=B0=95=20=EC=9D=B8?=
 =?UTF-8?q?=EC=9B=90=20=EA=B0=92=20=EA=B0=9D=EC=B2=B4=20Capacity=20?=
 =?UTF-8?q?=EC=B6=94=EA=B0=80?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Capacity.java
- 최대 수강 인원을 표현하는 VO 추가
- 1명 이상인지 검증하는 로직 포함
- 0 이하 입력 시 IllegalArgumentException 발생

CapacityTest.java
- 정상 생성 테스트 추가
- 0 이하 입력 시 예외 발생 테스트 추가
---
 .../nextstep/courses/domain/Capacity.java     | 12 ++++++++++
 .../nextstep/courses/domain/CapacityTest.java | 23 +++++++++++++++++++
 2 files changed, 35 insertions(+)
 create mode 100644 src/main/java/nextstep/courses/domain/Capacity.java
 create mode 100644 src/test/java/nextstep/courses/domain/CapacityTest.java

diff --git a/src/main/java/nextstep/courses/domain/Capacity.java b/src/main/java/nextstep/courses/domain/Capacity.java
new file mode 100644
index 000000000..db2dd20ed
--- /dev/null
+++ b/src/main/java/nextstep/courses/domain/Capacity.java
@@ -0,0 +1,12 @@
+package nextstep.courses.domain;
+
+public class Capacity {
+    private final int value;
+
+    public Capacity(int value) {
+        if (value <= 0) {
+            throw new IllegalArgumentException(String.format("최대 수강 인원은 1명 이상이어야 합니다. (입력: %d)", value));
+        }
+        this.value = value;
+    }
+}
diff --git a/src/test/java/nextstep/courses/domain/CapacityTest.java b/src/test/java/nextstep/courses/domain/CapacityTest.java
new file mode 100644
index 000000000..ab6a1a1b1
--- /dev/null
+++ b/src/test/java/nextstep/courses/domain/CapacityTest.java
@@ -0,0 +1,23 @@
+package nextstep.courses.domain;
+
+import static org.assertj.core.api.Assertions.*;
+
+import org.junit.jupiter.api.DisplayNameGeneration;
+import org.junit.jupiter.api.DisplayNameGenerator;
+import org.junit.jupiter.api.Test;
+
+@DisplayNameGeneration(DisplayNameGenerator.ReplaceUnderscores.class)
+class CapacityTest {
+
+    @Test
+    void 생성자_정상입력_생성성공() {
+        assertThatCode(() -> new Capacity(1)).doesNotThrowAnyException();
+    }
+
+    @Test
+    void 생성자_0명이하_예외발생() {
+        assertThatThrownBy(() -> new Capacity(0))
+                .isInstanceOf(IllegalArgumentException.class)
+                .hasMessageContaining("최대 수강 인원은 1명 이상");
+    }
+}

From 3c2f1a63826957b0eaadf0545058e46c84ee346c Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 21:01:40 +0900
Subject: [PATCH 30/45] =?UTF-8?q?feat:=20Capacity=EC=97=90=20=EC=A0=95?=
 =?UTF-8?q?=EC=9B=90=20=EC=B4=88=EA=B3=BC=20=EC=97=AC=EB=B6=80=20=ED=8C=90?=
 =?UTF-8?q?=EB=8B=A8=20=EA=B8=B0=EB=8A=A5=20=EC=B6=94=EA=B0=80?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Capacity.java
- isOver(currentCount) 메서드 추가로 현재 인원 대비 정원 초과 여부 판단 기능 제공

CapacityTest.java
- isOver에 대한 파라미터화 테스트(CsvSource) 추가
- 정원 == 현재 인원 → 초과(true), 현재 인원 < 정원 → 미초과(false) 검증
---
 src/main/java/nextstep/courses/domain/Capacity.java   |  4 ++++
 .../java/nextstep/courses/domain/CapacityTest.java    | 11 +++++++++++
 2 files changed, 15 insertions(+)

diff --git a/src/main/java/nextstep/courses/domain/Capacity.java b/src/main/java/nextstep/courses/domain/Capacity.java
index db2dd20ed..b23515f9f 100644
--- a/src/main/java/nextstep/courses/domain/Capacity.java
+++ b/src/main/java/nextstep/courses/domain/Capacity.java
@@ -9,4 +9,8 @@ public Capacity(int value) {
         }
         this.value = value;
     }
+
+    public boolean isOver(int currentCount) {
+        return currentCount >= value;
+    }
 }
diff --git a/src/test/java/nextstep/courses/domain/CapacityTest.java b/src/test/java/nextstep/courses/domain/CapacityTest.java
index ab6a1a1b1..f7944ca95 100644
--- a/src/test/java/nextstep/courses/domain/CapacityTest.java
+++ b/src/test/java/nextstep/courses/domain/CapacityTest.java
@@ -5,6 +5,8 @@
 import org.junit.jupiter.api.DisplayNameGeneration;
 import org.junit.jupiter.api.DisplayNameGenerator;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
 
 @DisplayNameGeneration(DisplayNameGenerator.ReplaceUnderscores.class)
 class CapacityTest {
@@ -20,4 +22,13 @@ class CapacityTest {
                 .isInstanceOf(IllegalArgumentException.class)
                 .hasMessageContaining("최대 수강 인원은 1명 이상");
     }
+
+    @ParameterizedTest(name = "정원 {0}명 / 현재 {1}명 → 초과 여부: {2}")
+    @CsvSource({"10, 10, true", "10, 9, false"})
+    void isOver_정원초과여부_확인(int capacityValue, int currentCount, boolean expected) {
+        boolean result = new Capacity(capacityValue).isOver(currentCount);
+
+        // then
+        assertThat(result).isEqualTo(expected);
+    }
 }

From e7d1082980b3dfe5fa206acde5a2f810c3900234 Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 21:12:43 +0900
Subject: [PATCH 31/45] =?UTF-8?q?refactor:=20PaidSession=EC=97=90=EC=84=9C?=
 =?UTF-8?q?=20Capacity=C2=B7Money=20=EA=B0=92=20=EA=B0=9D=EC=B2=B4=20?=
 =?UTF-8?q?=EC=A0=81=EC=9A=A9=20=EB=B0=8F=20=ED=85=8C=EC=8A=A4=ED=8A=B8=20?=
 =?UTF-8?q?=EC=A0=95=EB=A6=AC?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Capacity.java
- getValue() 추가하여 정원 출력 가능하도록 확장

PaidSession.java
- 정원(capacity)와 수강료(price)를 VO(Capacity, Money)로 교체
- 기본 생성자에서 int 입력을 받아 VO로 변환하도록 변경
- 상태지정 생성자 역시 VO 기반 생성자로 연결
- validateCapacity에서 Capacity.isOver 사용하도록 변경
- 오류 메시지에서 capacity.getValue() 활용

PaidSessionTest.java
- 생성자 테스트를 VO 적용 후 시그니처 변경에 맞게 수정
- fee 제거 후 price 정수 기반 생성 구조로 변경
- enroll 관련 테스트 모두 업데이트된 시그니처에 맞게 수정
---
 .../nextstep/courses/domain/Capacity.java     |  4 +++
 .../nextstep/courses/domain/PaidSession.java  | 27 ++++++++-----------
 .../courses/domain/PaidSessionTest.java       | 21 +++------------
 3 files changed, 19 insertions(+), 33 deletions(-)

diff --git a/src/main/java/nextstep/courses/domain/Capacity.java b/src/main/java/nextstep/courses/domain/Capacity.java
index b23515f9f..dbfbab0bf 100644
--- a/src/main/java/nextstep/courses/domain/Capacity.java
+++ b/src/main/java/nextstep/courses/domain/Capacity.java
@@ -13,4 +13,8 @@ public Capacity(int value) {
     public boolean isOver(int currentCount) {
         return currentCount >= value;
     }
+
+    public int getValue() {
+        return this.value;
+    }
 }
diff --git a/src/main/java/nextstep/courses/domain/PaidSession.java b/src/main/java/nextstep/courses/domain/PaidSession.java
index e9f2400d7..b0f13d6ca 100644
--- a/src/main/java/nextstep/courses/domain/PaidSession.java
+++ b/src/main/java/nextstep/courses/domain/PaidSession.java
@@ -1,29 +1,24 @@
 package nextstep.courses.domain;
 
 public class PaidSession extends Session {
-    private final int capacity;
+    private final Capacity capacity;
     private final Money price;
 
-    public PaidSession(CoverImage coverImage, SessionPeriod period, int capacity, Money price) {
-        super(coverImage, period);
-        validateMaxEnrollment(capacity);
-        this.capacity = capacity;
-        this.price = price;
+    public PaidSession(CoverImage coverImage, SessionPeriod period, int capacity, int price) {
+        this(coverImage, period, SessionStatus.PREPARING, new Capacity(capacity), new Money(price));
+    }
+
+    public PaidSession(CoverImage coverImage, SessionPeriod period, SessionStatus status, int capacity, int price) {
+        this(coverImage, period, status, new Capacity(capacity), new Money(price));
     }
 
-    public PaidSession(CoverImage coverImage, SessionPeriod period, SessionStatus status, int capacity, Money price) {
+    public PaidSession(
+            CoverImage coverImage, SessionPeriod period, SessionStatus status, Capacity capacity, Money price) {
         super(coverImage, period, status);
-        validateMaxEnrollment(capacity);
         this.capacity = capacity;
         this.price = price;
     }
 
-    private void validateMaxEnrollment(int maxEnrollment) {
-        if (maxEnrollment <= 0) {
-            throw new IllegalArgumentException(String.format("최대 수강 인원은 1명 이상이어야 합니다. (입력: %d)", maxEnrollment));
-        }
-    }
-
     public void enroll(Enrollment enrollment, Money payment) {
         validatePayment(payment);
         validateCapacity();
@@ -37,8 +32,8 @@ private void validatePayment(Money payment) {
     }
 
     private void validateCapacity() {
-        if (enrollmentCount() >= capacity) {
-            throw new IllegalStateException(String.format("수강 인원이 초과되었습니다. (최대: %d명)", capacity));
+        if (this.capacity.isOver(enrollmentCount())) {
+            throw new IllegalStateException(String.format("수강 인원이 초과되었습니다. (최대: %d명)", capacity.getValue()));
         }
     }
 }
diff --git a/src/test/java/nextstep/courses/domain/PaidSessionTest.java b/src/test/java/nextstep/courses/domain/PaidSessionTest.java
index 9cfbc6471..f0b30bafd 100644
--- a/src/test/java/nextstep/courses/domain/PaidSessionTest.java
+++ b/src/test/java/nextstep/courses/domain/PaidSessionTest.java
@@ -14,34 +14,21 @@ class PaidSessionTest {
 
     private CoverImage coverImage;
     private SessionPeriod period;
-    private Money fee;
 
     @BeforeEach
     void setUp() {
         coverImage = new CoverImage("image.png", 1024, 300, 200);
         period = new SessionPeriod(LocalDate.of(2024, 1, 1), LocalDate.of(2024, 3, 31));
-        fee = new Money(50000);
     }
 
     @Test
     void 생성자_정상입력_생성성공() {
-        assertThatCode(() -> new PaidSession(coverImage, period, 30, fee)).doesNotThrowAnyException();
-    }
-
-    @Test
-    void 생성자_최대인원0명_예외발생() {
-        CoverImage coverImage = new CoverImage("image.png", 1024, 300, 200);
-        SessionPeriod period = new SessionPeriod(LocalDate.of(2024, 1, 1), LocalDate.of(2024, 3, 31));
-        Money fee = new Money(50000);
-
-        assertThatThrownBy(() -> new PaidSession(coverImage, period, 0, fee))
-                .isInstanceOf(IllegalArgumentException.class)
-                .hasMessageContaining("최대 수강 인원은 1명 이상");
+        assertThatCode(() -> new PaidSession(coverImage, period, 30, 50000)).doesNotThrowAnyException();
     }
 
     @Test
     void enroll_정상입력_성공() {
-        PaidSession session = new PaidSession(coverImage, period, SessionStatus.RECRUITING, 3, fee);
+        PaidSession session = new PaidSession(coverImage, period, SessionStatus.RECRUITING, 3, 50000);
         Enrollment enrollment = new Enrollment(1L, 1L, LocalDateTime.now());
         Money payment = new Money(50000);
 
@@ -52,7 +39,7 @@ void setUp() {
 
     @Test
     void enroll_결제금액불일치_예외발생() {
-        PaidSession session = new PaidSession(coverImage, period, SessionStatus.RECRUITING, 3, fee);
+        PaidSession session = new PaidSession(coverImage, period, SessionStatus.RECRUITING, 3, 50000);
         Enrollment enrollment = new Enrollment(1L, 1L, LocalDateTime.now());
         Money wrongPayment = new Money(30000);
 
@@ -63,7 +50,7 @@ void setUp() {
 
     @Test
     void enroll_인원초과_예외발생() {
-        PaidSession session = new PaidSession(coverImage, period, SessionStatus.RECRUITING, 2, fee);
+        PaidSession session = new PaidSession(coverImage, period, SessionStatus.RECRUITING, 2, 50000);
         Money payment = new Money(50000);
 
         session.enroll(new Enrollment(1L, 1L, LocalDateTime.now()), payment);

From 99f90a8f368c4264825212ed91a558710b848fab Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 21:27:42 +0900
Subject: [PATCH 32/45] =?UTF-8?q?refactor:=20Course=C2=B7Enrollment=20?=
 =?UTF-8?q?=EB=B6=88=EB=B3=80=EC=84=B1=20=EA=B0=95=ED=99=94?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Course.java
- createdAt, updatedAt 필드를 final로 변경하여 생성 시점 이후 변경 불가하도록 개선

Enrollment.java
- id, sessionId, studentId, createdAt 필드를 final로 변경해 불변 객체로 전환
- 생성자 외에는 상태가 변하지 않도록 구조 명확화
---
 src/main/java/nextstep/courses/domain/Course.java     | 4 ++--
 src/main/java/nextstep/courses/domain/Enrollment.java | 8 ++++----
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/src/main/java/nextstep/courses/domain/Course.java b/src/main/java/nextstep/courses/domain/Course.java
index f3083f9e3..06fe9b5ff 100644
--- a/src/main/java/nextstep/courses/domain/Course.java
+++ b/src/main/java/nextstep/courses/domain/Course.java
@@ -11,9 +11,9 @@ public class Course {
 
     private final Sessions sessions;
 
-    private LocalDateTime createdAt;
+    private final LocalDateTime createdAt;
 
-    private LocalDateTime updatedAt;
+    private final LocalDateTime updatedAt;
 
     public Course(String title, Long creatorId, LocalDateTime now) {
         this(0L, title, creatorId, new Sessions(), now, null);
diff --git a/src/main/java/nextstep/courses/domain/Enrollment.java b/src/main/java/nextstep/courses/domain/Enrollment.java
index 91bee250e..18077f13f 100644
--- a/src/main/java/nextstep/courses/domain/Enrollment.java
+++ b/src/main/java/nextstep/courses/domain/Enrollment.java
@@ -3,10 +3,10 @@
 import java.time.LocalDateTime;
 
 public class Enrollment {
-    private Long id;
-    private Long sessionId;
-    private Long studentId;
-    private LocalDateTime createdAt;
+    private final Long id;
+    private final Long sessionId;
+    private final Long studentId;
+    private final LocalDateTime createdAt;
 
     public Enrollment(Long sessionId, Long studentId, LocalDateTime now) {
         this(0L, sessionId, studentId, now);

From c65b23a1065fd94e640f2501e078752f5d808202 Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 21:37:32 +0900
Subject: [PATCH 33/45] =?UTF-8?q?refactor:=20Session=20=EB=B6=88=EB=B3=80?=
 =?UTF-8?q?=20=ED=95=84=EB=93=9C=20=EC=A0=81=EC=9A=A9=20=EB=B0=8F=20?=
 =?UTF-8?q?=ED=85=8C=EC=8A=A4=ED=8A=B8=20=EC=A3=BC=EC=84=9D=20=EC=A0=95?=
 =?UTF-8?q?=EB=A6=AC?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Session.java
- id, coverImage, period, status 필드를 final로 변경하여 불변성 강화
- 생성 후 변경 불가능한 도메인 모델로 구조 개선

CapacityTest.java
- 불필요한 주석 제거로 테스트 코드 간결화
---
 src/main/java/nextstep/courses/domain/Session.java      | 8 ++++----
 src/test/java/nextstep/courses/domain/CapacityTest.java | 1 -
 2 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/src/main/java/nextstep/courses/domain/Session.java b/src/main/java/nextstep/courses/domain/Session.java
index 6c8eb8a6a..879fcc906 100644
--- a/src/main/java/nextstep/courses/domain/Session.java
+++ b/src/main/java/nextstep/courses/domain/Session.java
@@ -1,10 +1,10 @@
 package nextstep.courses.domain;
 
 public abstract class Session {
-    private Long id;
-    private CoverImage coverImage;
-    private SessionPeriod period;
-    private SessionStatus status;
+    private final Long id;
+    private final CoverImage coverImage;
+    private final SessionPeriod period;
+    private final SessionStatus status;
     private final Enrollments enrollments;
 
     public Session(CoverImage coverImage, SessionPeriod period) {
diff --git a/src/test/java/nextstep/courses/domain/CapacityTest.java b/src/test/java/nextstep/courses/domain/CapacityTest.java
index f7944ca95..6be60f0ba 100644
--- a/src/test/java/nextstep/courses/domain/CapacityTest.java
+++ b/src/test/java/nextstep/courses/domain/CapacityTest.java
@@ -28,7 +28,6 @@ class CapacityTest {
     void isOver_정원초과여부_확인(int capacityValue, int currentCount, boolean expected) {
         boolean result = new Capacity(capacityValue).isOver(currentCount);
 
-        // then
         assertThat(result).isEqualTo(expected);
     }
 }

From 10d47c2576262463238e9f290aa5d500f8ccc095 Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 21:39:32 +0900
Subject: [PATCH 34/45] =?UTF-8?q?docs:=20=EB=8F=84=EB=A9=94=EC=9D=B8=20?=
 =?UTF-8?q?=EB=AA=A8=EB=8D=B8=20=EB=AC=B8=EC=84=9C=EC=97=90=20=EA=B7=9C?=
 =?UTF-8?q?=EC=B9=99=C2=B7=EC=B2=B4=ED=81=AC=EB=A6=AC=EC=8A=A4=ED=8A=B8?=
 =?UTF-8?q?=C2=B7=EA=B5=AC=ED=98=84=20=EB=AA=A9=EB=A1=9D=20=EC=B6=94?=
 =?UTF-8?q?=EA=B0=80?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

- 규칙 7(인스턴스 변수 3개 제한)을 명시적으로 문서에 포함해 설계 기준 강화
- PR 전 점검 섹션 추가 및 체크리스트 파일 링크 연결
- 전체 도메인 기능 구현 목록을 항목별로 정리해 진행 상황을 명확하게 표현
- Course, Session, Value Objects, 일급 컬렉션, Enum 등 모든 구성 요소의 요구 기능을 체크리스트 형태로 문서화
---
 docs/02-lms-domain-model.md | 60 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 59 insertions(+), 1 deletion(-)

diff --git a/docs/02-lms-domain-model.md b/docs/02-lms-domain-model.md
index 234e52c03..ebec46a9d 100644
--- a/docs/02-lms-domain-model.md
+++ b/docs/02-lms-domain-model.md
@@ -8,6 +8,7 @@
 - 객체지향 생활 체조 원칙 준수
 - 테스트 작성하기 쉬운 구조로 설계
 - 자기 점검 체크리스트 준수
+- 특히 "규칙 7: 3개 이상의 인스턴스 변수를 가진 클래스를 쓰지 않는다."를 지키기 위해 노력한다. 
 ## 학습 관리 시스템(LMS)
 - 넥스트스텝은 재직자를 대상으로 소프트웨어 교육을 진행하는 교육 기관이다.
 - 2018년 교육 사업을 시작했다.
@@ -30,4 +31,61 @@
 ## 프로그래밍 요구사항
 - DB 테이블 설꼐 없이 도메인 모델부터 구현한다.
 - 도메인 모델은 TDD로 구현한다.
-  - 단, Service 클래스는 단위 테스트가 없어도 된다.
\ No newline at end of file
+  - 단, Service 클래스는 단위 테스트가 없어도 된다.
+## PR 전 점검
+**[체크리스트 확인하기](checklist.md)**
+## 구현 기능 목록
+#### Course
+- [x] 강의 추가
+- [x] 강의 개수 조회
+
+#### Sessions (일급 컬렉션)
+- [x] 강의 추가
+- [x] 강의 개수 조회
+
+#### Session (abstract)
+- [x] 수강 신청
+  - [x] 모집중 상태 검증
+- [x] 수강 인원 조회
+
+#### FreeSession
+- [x] Session 상속
+#### PaidSession
+- [x] 수강 신청
+  - [x] 결제 금액 검증
+  - [x] 수강 인원 검증
+  - [x] 부모 수강 신청 호출
+
+#### Enrollments (일급 컬렉션)
+- [x] 수강 신청 추가
+- [x] 수강 인원 조회
+
+#### CoverImage (VO)
+- [x] 이미지 파일 정보와 크기 정보 조합 생성
+
+#### ImageFile (VO)
+- [x] 파일 크기 검증 (1MB 이하)
+- [x] 확장자 추출
+- [x] 이미지 타입 변환
+
+#### ImageDimension (VO)
+- [x] 너비/높이 최소값 검증 (300x200 이상)
+- [x] 비율 검증 (3:2)
+
+#### ImageType (Enum)
+- [x] 확장자 → ImageType 변환 (from(String))
+- [x] JPEG → JPG 변환 지원
+
+#### SessionPeriod (VO)
+- [x] 시작일/종료일 검증 (종료일 >= 시작일)
+
+#### SessionStatus (Enum)
+- [x] 수강 신청 가능 여부
+
+#### Money (VO)
+- [x] 금액 검증 (0 이상)
+- [x] 금액 비교
+
+#### Capacity (VO)
+- [x] 최대 인원 검증 (1명 이상)
+- [x] 초과 여부 확인

From c6e13baa9efc35fc9750015e269c4525c6c33ac1 Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 21:54:29 +0900
Subject: [PATCH 35/45] =?UTF-8?q?docs:=20PR=20=EB=A7=81=ED=81=AC=20?=
 =?UTF-8?q?=EC=B6=94=EA=B0=80?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 docs/02-lms-domain-model.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/02-lms-domain-model.md b/docs/02-lms-domain-model.md
index ebec46a9d..86fbc69c2 100644
--- a/docs/02-lms-domain-model.md
+++ b/docs/02-lms-domain-model.md
@@ -2,7 +2,7 @@
 ***
 ## 코드 리뷰
 > PR 링크:
-> 
+> **[https://github.com/next-step/java-lms/pull/811](https://github.com/next-step/java-lms/pull/811)**
 ## 나의 학습 목표
 - TDD 사이클로 구현
 - 객체지향 생활 체조 원칙 준수

From e39012da09cdbcdc76add9d834648175e30bffaa Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 22:37:20 +0900
Subject: [PATCH 36/45] =?UTF-8?q?feat:=20=EC=88=98=EA=B0=95=20=EC=8B=A0?=
 =?UTF-8?q?=EC=B2=AD=20=EC=A4=91=EB=B3=B5=20=EA=B2=80=EC=A6=9D=20=EC=B6=94?=
 =?UTF-8?q?=EA=B0=80?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Enrollment.java
- studentId 조회를 위한 getter 추가

Enrollments.java
- add 시 중복 수강 신청 여부 검증 추가
- 동일 studentId 존재 시 예외 발생 처리

EnrollmentsTest.java
- 정상 추가 테스트 작성
- 중복 신청 시 예외 검증 테스트 추가
---
 .../nextstep/courses/domain/Enrollment.java   |  4 ++
 .../nextstep/courses/domain/Enrollments.java  |  8 ++++
 .../courses/domain/EnrollmentsTest.java       | 38 +++++++++++++++++++
 3 files changed, 50 insertions(+)
 create mode 100644 src/test/java/nextstep/courses/domain/EnrollmentsTest.java

diff --git a/src/main/java/nextstep/courses/domain/Enrollment.java b/src/main/java/nextstep/courses/domain/Enrollment.java
index 18077f13f..28442d304 100644
--- a/src/main/java/nextstep/courses/domain/Enrollment.java
+++ b/src/main/java/nextstep/courses/domain/Enrollment.java
@@ -18,4 +18,8 @@ public Enrollment(Long id, Long sessionId, Long studentId, LocalDateTime created
         this.studentId = studentId;
         this.createdAt = createdAt;
     }
+
+    public Long getStudentId() {
+        return studentId;
+    }
 }
diff --git a/src/main/java/nextstep/courses/domain/Enrollments.java b/src/main/java/nextstep/courses/domain/Enrollments.java
index ebb07909c..147337a46 100644
--- a/src/main/java/nextstep/courses/domain/Enrollments.java
+++ b/src/main/java/nextstep/courses/domain/Enrollments.java
@@ -15,9 +15,17 @@ public Enrollments(List<Enrollment> values) {
     }
 
     public void add(Enrollment enrollment) {
+        validateNotDuplicate(enrollment);
         this.values.add(enrollment);
     }
 
+    private void validateNotDuplicate(Enrollment enrollment) {
+        boolean exists = values.stream().anyMatch(e -> e.getStudentId().equals(enrollment.getStudentId()));
+        if (exists) {
+            throw new IllegalArgumentException("이미 수강 신청한 강의입니다.");
+        }
+    }
+
     public int count() {
         return this.values.size();
     }
diff --git a/src/test/java/nextstep/courses/domain/EnrollmentsTest.java b/src/test/java/nextstep/courses/domain/EnrollmentsTest.java
new file mode 100644
index 000000000..3bee9fd89
--- /dev/null
+++ b/src/test/java/nextstep/courses/domain/EnrollmentsTest.java
@@ -0,0 +1,38 @@
+package nextstep.courses.domain;
+
+import static org.assertj.core.api.Assertions.*;
+
+import java.time.LocalDateTime;
+import org.junit.jupiter.api.DisplayNameGeneration;
+import org.junit.jupiter.api.DisplayNameGenerator;
+import org.junit.jupiter.api.Test;
+
+@DisplayNameGeneration(DisplayNameGenerator.ReplaceUnderscores.class)
+class EnrollmentsTest {
+
+    @Test
+    void add_정상입력_성공() {
+        var e1 = new Enrollment(1L, 1L, LocalDateTime.now());
+        var e2 = new Enrollment(1L, 2L, LocalDateTime.now());
+        var enrollments = new Enrollments();
+
+        assertThatCode(() -> {
+                    enrollments.add(e1);
+                    enrollments.add(e2);
+                })
+                .doesNotThrowAnyException();
+    }
+
+    @Test
+    void add_중복신청_예외발생() {
+        var enrollment = new Enrollment(1L, 1L, LocalDateTime.now());
+        var enrollments = new Enrollments();
+
+        assertThatThrownBy(() -> {
+                    enrollments.add(enrollment);
+                    enrollments.add(enrollment);
+                })
+                .isInstanceOf(IllegalArgumentException.class)
+                .hasMessage("이미 수강 신청한 강의입니다.");
+    }
+}

From 1fb78b798e62e7a28148b162e22a8e7d94663ed6 Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 22:56:58 +0900
Subject: [PATCH 37/45] =?UTF-8?q?refactor:=20Session=20=EC=88=98=EA=B0=95?=
 =?UTF-8?q?=EC=8B=A0=EC=B2=AD=20=ED=85=9C=ED=94=8C=EB=A6=BF=20=EB=A9=94?=
 =?UTF-8?q?=EC=84=9C=EB=93=9C=20=ED=8C=A8=ED=84=B4=20=EC=A0=81=EC=9A=A9?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

FreeSession.java
- 결제/정원 정책 메서드 빈 구현 추가(무료 세션 특성 반영)

Money.java
- ZERO 상수 추가로 무료 결제 표현 단순화

PaidSession.java
- 결제 검증을 validatePaymentPolicy로 이관
- 정원 검증을 validateCapacityPolicy로 이관

Session.java
- enroll 메서드 final 처리 및 템플릿 메서드 패턴 적용
- validatePaymentPolicy, validateCapacityPolicy 추상 메서드 정의

SessionTest.java
- 무료 세션 enroll 테스트에서 Money.ZERO 사용하도록 수정
- 상태 검증 테스트도 동일하게 Money.ZERO 적용
---
 .../java/nextstep/courses/domain/FreeSession.java    |  6 ++++++
 src/main/java/nextstep/courses/domain/Money.java     |  2 ++
 .../java/nextstep/courses/domain/PaidSession.java    | 12 ++++--------
 src/main/java/nextstep/courses/domain/Session.java   |  8 +++++++-
 .../java/nextstep/courses/domain/SessionTest.java    |  4 ++--
 5 files changed, 21 insertions(+), 11 deletions(-)

diff --git a/src/main/java/nextstep/courses/domain/FreeSession.java b/src/main/java/nextstep/courses/domain/FreeSession.java
index 283d2c219..d8753d33a 100644
--- a/src/main/java/nextstep/courses/domain/FreeSession.java
+++ b/src/main/java/nextstep/courses/domain/FreeSession.java
@@ -8,4 +8,10 @@ public FreeSession(CoverImage coverImage, SessionPeriod period) {
     public FreeSession(CoverImage coverImage, SessionPeriod period, SessionStatus status) {
         super(coverImage, period, status);
     }
+
+    @Override
+    protected void validatePaymentPolicy(Money payment) {}
+
+    @Override
+    protected void validateCapacityPolicy() {}
 }
diff --git a/src/main/java/nextstep/courses/domain/Money.java b/src/main/java/nextstep/courses/domain/Money.java
index 4dc3bfd7f..770938861 100644
--- a/src/main/java/nextstep/courses/domain/Money.java
+++ b/src/main/java/nextstep/courses/domain/Money.java
@@ -1,6 +1,8 @@
 package nextstep.courses.domain;
 
 public class Money {
+    public static final Money ZERO = new Money(0);
+
     private final int amount;
 
     public Money(int amount) {
diff --git a/src/main/java/nextstep/courses/domain/PaidSession.java b/src/main/java/nextstep/courses/domain/PaidSession.java
index b0f13d6ca..891bb8b00 100644
--- a/src/main/java/nextstep/courses/domain/PaidSession.java
+++ b/src/main/java/nextstep/courses/domain/PaidSession.java
@@ -19,19 +19,15 @@ public PaidSession(
         this.price = price;
     }
 
-    public void enroll(Enrollment enrollment, Money payment) {
-        validatePayment(payment);
-        validateCapacity();
-        super.enroll(enrollment);
-    }
-
-    private void validatePayment(Money payment) {
+    @Override
+    protected void validatePaymentPolicy(Money payment) {
         if (!price.isSameAs(payment)) {
             throw new IllegalArgumentException("결제 금액이 수강료와 일치하지 않습니다.");
         }
     }
 
-    private void validateCapacity() {
+    @Override
+    protected void validateCapacityPolicy() {
         if (this.capacity.isOver(enrollmentCount())) {
             throw new IllegalStateException(String.format("수강 인원이 초과되었습니다. (최대: %d명)", capacity.getValue()));
         }
diff --git a/src/main/java/nextstep/courses/domain/Session.java b/src/main/java/nextstep/courses/domain/Session.java
index 879fcc906..dfa148956 100644
--- a/src/main/java/nextstep/courses/domain/Session.java
+++ b/src/main/java/nextstep/courses/domain/Session.java
@@ -24,8 +24,10 @@ public Session(
         this.enrollments = enrollments;
     }
 
-    public void enroll(Enrollment enrollment) {
+    public final void enroll(Enrollment enrollment, Money payment) {
         validateStatus();
+        validatePaymentPolicy(payment);
+        validateCapacityPolicy();
         enrollments.add(enrollment);
     }
 
@@ -35,6 +37,10 @@ protected void validateStatus() {
         }
     }
 
+    protected abstract void validatePaymentPolicy(Money payment);
+
+    protected abstract void validateCapacityPolicy();
+
     public int enrollmentCount() {
         return enrollments.count();
     }
diff --git a/src/test/java/nextstep/courses/domain/SessionTest.java b/src/test/java/nextstep/courses/domain/SessionTest.java
index 5dabf0870..2d4a052ed 100644
--- a/src/test/java/nextstep/courses/domain/SessionTest.java
+++ b/src/test/java/nextstep/courses/domain/SessionTest.java
@@ -34,7 +34,7 @@ void setUp() {
         Session session = new FreeSession(coverImage, period, SessionStatus.RECRUITING);
         Enrollment enrollment = new Enrollment(1L, 1L, LocalDateTime.now());
 
-        session.enroll(enrollment);
+        session.enroll(enrollment, Money.ZERO);
 
         assertThat(session.enrollmentCount()).isEqualTo(1);
     }
@@ -47,7 +47,7 @@ void setUp() {
         Session session = new FreeSession(coverImage, period, status);
         Enrollment enrollment = new Enrollment(1L, 1L, LocalDateTime.now());
 
-        assertThatThrownBy(() -> session.enroll(enrollment))
+        assertThatThrownBy(() -> session.enroll(enrollment, Money.ZERO))
                 .isInstanceOf(IllegalStateException.class)
                 .hasMessageContaining("모집중인 강의만");
     }

From 28c9199d5190f45280c2c2dfb75c450d6f39cd7a Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 23:10:31 +0900
Subject: [PATCH 38/45] =?UTF-8?q?test:=20FreeSession=20=EC=A0=84=EC=9A=A9?=
 =?UTF-8?q?=20=ED=85=8C=EC=8A=A4=ED=8A=B8=20=ED=99=95=EC=9E=A5=20=EB=B0=8F?=
 =?UTF-8?q?=20SessionTest=20=EC=82=AD=EC=A0=9C?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

FreeSessionTest.java
- 공통 픽스처 setUp 추가
- 모집중 수강 신청 성공 테스트 추가
- 상태별(준비중/종료) 수강 신청 실패 테스트 추가
- 기존 생성자 검증 로직 유지 및 보강

SessionTest.java
- FreeSessionTest로 통합됨에 따라 클래스 삭제
---
 .../courses/domain/FreeSessionTest.java       | 42 +++++++++++++--
 .../nextstep/courses/domain/SessionTest.java  | 54 -------------------
 2 files changed, 39 insertions(+), 57 deletions(-)
 delete mode 100644 src/test/java/nextstep/courses/domain/SessionTest.java

diff --git a/src/test/java/nextstep/courses/domain/FreeSessionTest.java b/src/test/java/nextstep/courses/domain/FreeSessionTest.java
index e9751f43f..63f9c815a 100644
--- a/src/test/java/nextstep/courses/domain/FreeSessionTest.java
+++ b/src/test/java/nextstep/courses/domain/FreeSessionTest.java
@@ -3,18 +3,54 @@
 import static org.assertj.core.api.Assertions.*;
 
 import java.time.LocalDate;
+import java.time.LocalDateTime;
+import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.DisplayNameGeneration;
 import org.junit.jupiter.api.DisplayNameGenerator;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.EnumSource;
 
 @DisplayNameGeneration(DisplayNameGenerator.ReplaceUnderscores.class)
 class FreeSessionTest {
 
+    private CoverImage coverImage;
+    private SessionPeriod period;
+
+    @BeforeEach
+    void setUp() {
+        coverImage = new CoverImage("image.png", 1024, 300, 200);
+        period = new SessionPeriod(LocalDate.of(2024, 1, 1), LocalDate.of(2024, 3, 31));
+    }
+
     @Test
     void 생성자_정상입력_생성성공() {
-        CoverImage coverImage = new CoverImage("image.png", 1024, 300, 200);
-        SessionPeriod sessionPeriod = new SessionPeriod(LocalDate.of(2024, 1, 1), LocalDate.of(2024, 3, 31));
+        FreeSession session = new FreeSession(coverImage, period);
+
+        assertThat(session.getStatus()).isEqualTo(SessionStatus.PREPARING);
+    }
+
+    @Test
+    void enroll_모집중_성공() {
+        Session session = new FreeSession(coverImage, period, SessionStatus.RECRUITING);
+        Enrollment enrollment = new Enrollment(1L, 1L, LocalDateTime.now());
+
+        session.enroll(enrollment, Money.ZERO);
+
+        assertThat(session.enrollmentCount()).isEqualTo(1);
+    }
+
+    @ParameterizedTest(name = "상태:{0}")
+    @EnumSource(
+            value = SessionStatus.class,
+            names = {"PREPARING", "CLOSED"})
+    void enroll_모집중이아닐시_예외발생(SessionStatus status) {
+        FreeSession session = new FreeSession(coverImage, period, status);
+
+        Enrollment enrollment = new Enrollment(1L, 1L, LocalDateTime.now());
 
-        assertThatCode(() -> new FreeSession(coverImage, sessionPeriod)).doesNotThrowAnyException();
+        assertThatThrownBy(() -> session.enroll(enrollment, Money.ZERO))
+                .isInstanceOf(IllegalStateException.class)
+                .hasMessageContaining("모집중인 강의만");
     }
 }
diff --git a/src/test/java/nextstep/courses/domain/SessionTest.java b/src/test/java/nextstep/courses/domain/SessionTest.java
deleted file mode 100644
index 2d4a052ed..000000000
--- a/src/test/java/nextstep/courses/domain/SessionTest.java
+++ /dev/null
@@ -1,54 +0,0 @@
-package nextstep.courses.domain;
-
-import static org.assertj.core.api.Assertions.*;
-
-import java.time.LocalDate;
-import java.time.LocalDateTime;
-import org.junit.jupiter.api.BeforeEach;
-import org.junit.jupiter.api.DisplayNameGeneration;
-import org.junit.jupiter.api.DisplayNameGenerator;
-import org.junit.jupiter.api.Test;
-import org.junit.jupiter.params.ParameterizedTest;
-import org.junit.jupiter.params.provider.EnumSource;
-
-@DisplayNameGeneration(DisplayNameGenerator.ReplaceUnderscores.class)
-class SessionTest {
-    private CoverImage coverImage;
-    private SessionPeriod period;
-
-    @BeforeEach
-    void setUp() {
-        coverImage = new CoverImage("image.png", 1024, 300, 200);
-        period = new SessionPeriod(LocalDate.of(2024, 1, 1), LocalDate.of(2024, 3, 31));
-    }
-
-    @Test
-    void 생성자_정상입력_준비중상태() {
-        Session session = new FreeSession(coverImage, period);
-
-        assertThat(session.getStatus()).isEqualTo(SessionStatus.PREPARING);
-    }
-
-    @Test
-    void enroll_모집중_성공() {
-        Session session = new FreeSession(coverImage, period, SessionStatus.RECRUITING);
-        Enrollment enrollment = new Enrollment(1L, 1L, LocalDateTime.now());
-
-        session.enroll(enrollment, Money.ZERO);
-
-        assertThat(session.enrollmentCount()).isEqualTo(1);
-    }
-
-    @ParameterizedTest(name = "상태:{0}")
-    @EnumSource(
-            value = SessionStatus.class,
-            names = {"PREPARING", "CLOSED"})
-    void enroll_모집중이아닐시_예외발생(SessionStatus status) {
-        Session session = new FreeSession(coverImage, period, status);
-        Enrollment enrollment = new Enrollment(1L, 1L, LocalDateTime.now());
-
-        assertThatThrownBy(() -> session.enroll(enrollment, Money.ZERO))
-                .isInstanceOf(IllegalStateException.class)
-                .hasMessageContaining("모집중인 강의만");
-    }
-}

From 2fdb686a6c8e8c993dd12af1af220ef2294c7409 Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 23:19:22 +0900
Subject: [PATCH 39/45] =?UTF-8?q?test:=20=EC=83=9D=EC=84=B1=EC=9E=90=20?=
 =?UTF-8?q?=EB=B0=8F=20=EC=88=98=EA=B0=95=EC=8B=A0=EC=B2=AD=20=ED=85=8C?=
 =?UTF-8?q?=EC=8A=A4=ED=8A=B8=20=EA=B0=84=EA=B2=B0=ED=99=94?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

FreeSessionTest
- 생성자 검증을 한 줄로 축약하여 가독성 개선

PaidSessionTest
- 생성자 검증을 한 줄 표현으로 간결화
- 정상 수강 신청 테스트에서 payment 변수 제거 → 즉시 new Money() 전달
- 모집중이 아닐 때 실패 테스트 추가 (`EnumSource` 활용)
---
 .../courses/domain/FreeSessionTest.java       |  4 +---
 .../courses/domain/PaidSessionTest.java       | 21 ++++++++++++++++---
 2 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/src/test/java/nextstep/courses/domain/FreeSessionTest.java b/src/test/java/nextstep/courses/domain/FreeSessionTest.java
index 63f9c815a..6cc611b28 100644
--- a/src/test/java/nextstep/courses/domain/FreeSessionTest.java
+++ b/src/test/java/nextstep/courses/domain/FreeSessionTest.java
@@ -25,9 +25,7 @@ void setUp() {
 
     @Test
     void 생성자_정상입력_생성성공() {
-        FreeSession session = new FreeSession(coverImage, period);
-
-        assertThat(session.getStatus()).isEqualTo(SessionStatus.PREPARING);
+        assertThat(new FreeSession(coverImage, period).getStatus()).isEqualTo(SessionStatus.PREPARING);
     }
 
     @Test
diff --git a/src/test/java/nextstep/courses/domain/PaidSessionTest.java b/src/test/java/nextstep/courses/domain/PaidSessionTest.java
index f0b30bafd..4321181d0 100644
--- a/src/test/java/nextstep/courses/domain/PaidSessionTest.java
+++ b/src/test/java/nextstep/courses/domain/PaidSessionTest.java
@@ -8,6 +8,8 @@
 import org.junit.jupiter.api.DisplayNameGeneration;
 import org.junit.jupiter.api.DisplayNameGenerator;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.EnumSource;
 
 @DisplayNameGeneration(DisplayNameGenerator.ReplaceUnderscores.class)
 class PaidSessionTest {
@@ -23,16 +25,15 @@ void setUp() {
 
     @Test
     void 생성자_정상입력_생성성공() {
-        assertThatCode(() -> new PaidSession(coverImage, period, 30, 50000)).doesNotThrowAnyException();
+        assertThat(new PaidSession(coverImage, period, 30, 50000).getStatus()).isEqualTo(SessionStatus.PREPARING);
     }
 
     @Test
     void enroll_정상입력_성공() {
         PaidSession session = new PaidSession(coverImage, period, SessionStatus.RECRUITING, 3, 50000);
         Enrollment enrollment = new Enrollment(1L, 1L, LocalDateTime.now());
-        Money payment = new Money(50000);
 
-        session.enroll(enrollment, payment);
+        session.enroll(enrollment, new Money(50000));
 
         assertThat(session.enrollmentCount()).isEqualTo(1);
     }
@@ -60,4 +61,18 @@ void setUp() {
                 .isInstanceOf(IllegalStateException.class)
                 .hasMessageContaining("수강 인원이 초과");
     }
+
+    @ParameterizedTest(name = "상태:{0}")
+    @EnumSource(
+            value = SessionStatus.class,
+            names = {"PREPARING", "CLOSED"})
+    void enroll_모집중이아닐시_예외발생(SessionStatus status) {
+        PaidSession session = new PaidSession(coverImage, period, status, 2, 50000);
+
+        Enrollment enrollment = new Enrollment(1L, 1L, LocalDateTime.now());
+
+        assertThatThrownBy(() -> session.enroll(enrollment, Money.ZERO))
+                .isInstanceOf(IllegalStateException.class)
+                .hasMessageContaining("모집중인 강의만");
+    }
 }

From d0f4f1a88c96de47d8bea6109161b6a367909900 Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Wed, 10 Dec 2025 23:25:08 +0900
Subject: [PATCH 40/45] =?UTF-8?q?docs:=20=EC=84=B8=EC=85=98=20=EA=B5=AC?=
 =?UTF-8?q?=EC=A1=B0=20=EB=B0=8F=20=ED=85=9C=ED=94=8C=EB=A6=BF=20=EB=A9=94?=
 =?UTF-8?q?=EC=84=9C=EB=93=9C=20=ED=8C=A8=ED=84=B4=20=EC=A0=81=EC=9A=A9=20?=
 =?UTF-8?q?=EB=82=B4=EC=9A=A9=20=EC=97=85=EB=8D=B0=EC=9D=B4=ED=8A=B8?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

02-lms-domain-model.md
- Session을 추상 클래스 + 템플릿 메서드 패턴 적용 방식으로 상세화
- FreeSession/PaidSession의 정책 검증 구조와 구현 방식 설명 추가
- Enrollments의 중복 수강 신청 검증 항목 추가
---
 docs/02-lms-domain-model.md | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/docs/02-lms-domain-model.md b/docs/02-lms-domain-model.md
index 86fbc69c2..fd98f596a 100644
--- a/docs/02-lms-domain-model.md
+++ b/docs/02-lms-domain-model.md
@@ -43,22 +43,29 @@
 - [x] 강의 추가
 - [x] 강의 개수 조회
 
-#### Session (abstract)
-- [x] 수강 신청
+#### Session (추상 클래스, 템플릿 메서드 패턴 적용)
+- [x] 수강 신청 – 템플릿 메서드 방식
+  - [x] `final` enroll(enrollment, payment) 정의 
   - [x] 모집중 상태 검증
+  - [x] 결제 정책 검증 – 하위에서 구현 (validatePaymentPolicy)
+  - [x] 정원 정책 검증 – 하위에서 구현 (validateCapacityPolicy)
 - [x] 수강 인원 조회
 
 #### FreeSession
 - [x] Session 상속
+- [x] 수강 신청
+  - [x] 결제 정책 없음 → validatePaymentPolicy(): 빈 구현
+  - [x] 정원 정책 없음 → validateCapacityPolicy(): 빈 구현
 #### PaidSession
+- [x] Session 상속
 - [x] 수강 신청
   - [x] 결제 금액 검증
   - [x] 수강 인원 검증
-  - [x] 부모 수강 신청 호출
 
 #### Enrollments (일급 컬렉션)
 - [x] 수강 신청 추가
 - [x] 수강 인원 조회
+- [x] 중복 수강 신청 검증
 
 #### CoverImage (VO)
 - [x] 이미지 파일 정보와 크기 정보 조합 생성

From 900c8efa224264c04d58b0e6e85dc077b724c5de Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Thu, 11 Dec 2025 07:14:42 +0900
Subject: [PATCH 41/45] =?UTF-8?q?refactor:=20=EC=A4=91=EB=B3=B5=20?=
 =?UTF-8?q?=EC=88=98=EA=B0=95=20=EC=8B=A0=EC=B2=AD=20=EA=B2=80=EC=A6=9D=20?=
 =?UTF-8?q?=EB=A1=9C=EC=A7=81=20=EA=B0=84=EC=86=8C=ED=99=94?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Enrollments.java
- 중복 검증을 stream anyMatch → values.contains(enrollment) 방식으로 단순화
---
 src/main/java/nextstep/courses/domain/Enrollments.java | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/main/java/nextstep/courses/domain/Enrollments.java b/src/main/java/nextstep/courses/domain/Enrollments.java
index 147337a46..2be746d9b 100644
--- a/src/main/java/nextstep/courses/domain/Enrollments.java
+++ b/src/main/java/nextstep/courses/domain/Enrollments.java
@@ -20,8 +20,7 @@ public void add(Enrollment enrollment) {
     }
 
     private void validateNotDuplicate(Enrollment enrollment) {
-        boolean exists = values.stream().anyMatch(e -> e.getStudentId().equals(enrollment.getStudentId()));
-        if (exists) {
+        if (values.contains(enrollment)) {
             throw new IllegalArgumentException("이미 수강 신청한 강의입니다.");
         }
     }

From 8986d3b15e8b283030905caaade63a2152cd686b Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Thu, 11 Dec 2025 07:50:29 +0900
Subject: [PATCH 42/45] =?UTF-8?q?feat:=20=EC=88=98=EA=B0=95=20=EC=8B=A0?=
 =?UTF-8?q?=EC=B2=AD=20=EC=A0=95=EC=B1=85=20=EB=B6=84=EB=A6=AC=20=EB=B0=8F?=
 =?UTF-8?q?=20=EB=AC=B4=EB=A3=8C=20=EC=88=98=EA=B0=95=20=EC=A0=95=EC=B1=85?=
 =?UTF-8?q?=20=EA=B8=B0=EB=B3=B8=20=EA=B5=AC=ED=98=84=20=EC=B6=94=EA=B0=80?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

EnrollmentPolicy.java
- 템플릿 메서드 패턴 기반의 공통 검증 구조 도입
- 결제·정원 검증 메서드를 추상화하여 정책별 구현 가능하도록 설계

FreeEnrollmentPolicy.java
- 무료 강의용 정책 구현
- 결제·정원 검증을 비활성화
- FREE 타입 반환하도록 구현

SessionType.java
- FREE/PAID 세션 타입 정의 및 설명 필드 추가

FreeEnrollmentPolicyTest.java
- 무료 정책 검증 시 항상 성공하는지 테스트 추가
- 정책 타입이 FREE인지 검증하는 테스트 추가
---
 .../courses/domain/EnrollmentPolicy.java      | 14 +++++++++++
 .../courses/domain/FreeEnrollmentPolicy.java  | 19 +++++++++++++++
 .../nextstep/courses/domain/SessionType.java  | 12 ++++++++++
 .../domain/FreeEnrollmentPolicyTest.java      | 23 +++++++++++++++++++
 4 files changed, 68 insertions(+)
 create mode 100644 src/main/java/nextstep/courses/domain/EnrollmentPolicy.java
 create mode 100644 src/main/java/nextstep/courses/domain/FreeEnrollmentPolicy.java
 create mode 100644 src/main/java/nextstep/courses/domain/SessionType.java
 create mode 100644 src/test/java/nextstep/courses/domain/FreeEnrollmentPolicyTest.java

diff --git a/src/main/java/nextstep/courses/domain/EnrollmentPolicy.java b/src/main/java/nextstep/courses/domain/EnrollmentPolicy.java
new file mode 100644
index 000000000..360f18dc3
--- /dev/null
+++ b/src/main/java/nextstep/courses/domain/EnrollmentPolicy.java
@@ -0,0 +1,14 @@
+package nextstep.courses.domain;
+
+public abstract class EnrollmentPolicy {
+    public final void validate(Money payment, int currentCount) {
+        validatePayment(payment);
+        validateCapacity(currentCount);
+    }
+
+    public abstract SessionType getType();
+
+    protected abstract void validatePayment(Money payment);
+
+    protected abstract void validateCapacity(int currentCount);
+}
diff --git a/src/main/java/nextstep/courses/domain/FreeEnrollmentPolicy.java b/src/main/java/nextstep/courses/domain/FreeEnrollmentPolicy.java
new file mode 100644
index 000000000..84f4c150c
--- /dev/null
+++ b/src/main/java/nextstep/courses/domain/FreeEnrollmentPolicy.java
@@ -0,0 +1,19 @@
+package nextstep.courses.domain;
+
+public class FreeEnrollmentPolicy extends EnrollmentPolicy {
+
+    @Override
+    public SessionType getType() {
+        return SessionType.FREE;
+    }
+
+    @Override
+    protected void validatePayment(Money payment) {
+        // 무료는 검증 X
+    }
+
+    @Override
+    protected void validateCapacity(int currentCount) {
+        // 무료는 검증 X
+    }
+}
diff --git a/src/main/java/nextstep/courses/domain/SessionType.java b/src/main/java/nextstep/courses/domain/SessionType.java
new file mode 100644
index 000000000..21843f73e
--- /dev/null
+++ b/src/main/java/nextstep/courses/domain/SessionType.java
@@ -0,0 +1,12 @@
+package nextstep.courses.domain;
+
+public enum SessionType {
+    FREE("무료"),
+    PAID("유료");
+
+    SessionType(String description) {
+        this.description = description;
+    }
+
+    private final String description;
+}
diff --git a/src/test/java/nextstep/courses/domain/FreeEnrollmentPolicyTest.java b/src/test/java/nextstep/courses/domain/FreeEnrollmentPolicyTest.java
new file mode 100644
index 000000000..278cbd2fd
--- /dev/null
+++ b/src/test/java/nextstep/courses/domain/FreeEnrollmentPolicyTest.java
@@ -0,0 +1,23 @@
+package nextstep.courses.domain;
+
+import static org.assertj.core.api.Assertions.*;
+
+import org.junit.jupiter.api.DisplayNameGeneration;
+import org.junit.jupiter.api.DisplayNameGenerator;
+import org.junit.jupiter.api.Test;
+
+@DisplayNameGeneration(DisplayNameGenerator.ReplaceUnderscores.class)
+class FreeEnrollmentPolicyTest {
+
+    @Test
+    void validate_무료강의_항상성공() {
+        FreeEnrollmentPolicy policy = new FreeEnrollmentPolicy();
+
+        assertThatCode(() -> policy.validate(null, 1000000000)).doesNotThrowAnyException();
+    }
+
+    @Test
+    void getType_FREE_반환() {
+        assertThat(new FreeEnrollmentPolicy().getType()).isEqualTo(SessionType.FREE);
+    }
+}

From 3597f2ca8005e6f8b3dee118e6ca65b21f7481b5 Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Thu, 11 Dec 2025 07:56:17 +0900
Subject: [PATCH 43/45] =?UTF-8?q?feat:=20=EC=9C=A0=EB=A3=8C=20=EC=88=98?=
 =?UTF-8?q?=EA=B0=95=20=EC=A0=95=EC=B1=85(PaidEnrollmentPolicy)=20?=
 =?UTF-8?q?=EC=B6=94=EA=B0=80=20=EB=B0=8F=20=EA=B2=80=EC=A6=9D=20=ED=85=8C?=
 =?UTF-8?q?=EC=8A=A4=ED=8A=B8=20=EA=B5=AC=ED=98=84?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

PaidEnrollmentPolicy.java
- 유료 강의용 EnrollmentPolicy 구현
- 결제 금액 검증 로직 추가 (price.isSameAs)
- 정원 초과 검증 로직 추가 (capacity.isOver)
- PAID 타입 반환

PaidEnrollmentPolicyTest.java
- 정상 결제·정원 입력 시 성공 테스트 추가
- 결제 금액 불일치 시 예외 발생 테스트 추가
- 정원 초과 시 예외 발생 테스트 추가
- PAID 타입 반환 검증
---
 .../courses/domain/PaidEnrollmentPolicy.java  | 34 +++++++++++++++
 .../domain/PaidEnrollmentPolicyTest.java      | 43 +++++++++++++++++++
 2 files changed, 77 insertions(+)
 create mode 100644 src/main/java/nextstep/courses/domain/PaidEnrollmentPolicy.java
 create mode 100644 src/test/java/nextstep/courses/domain/PaidEnrollmentPolicyTest.java

diff --git a/src/main/java/nextstep/courses/domain/PaidEnrollmentPolicy.java b/src/main/java/nextstep/courses/domain/PaidEnrollmentPolicy.java
new file mode 100644
index 000000000..1f8895465
--- /dev/null
+++ b/src/main/java/nextstep/courses/domain/PaidEnrollmentPolicy.java
@@ -0,0 +1,34 @@
+package nextstep.courses.domain;
+
+public class PaidEnrollmentPolicy extends EnrollmentPolicy {
+    private final Capacity capacity;
+    private final Money price;
+
+    public PaidEnrollmentPolicy(int capacity, int price) {
+        this(new Capacity(capacity), new Money(price));
+    }
+
+    public PaidEnrollmentPolicy(Capacity capacity, Money price) {
+        this.capacity = capacity;
+        this.price = price;
+    }
+
+    @Override
+    public SessionType getType() {
+        return SessionType.PAID;
+    }
+
+    @Override
+    protected void validatePayment(Money payment) {
+        if (!price.isSameAs(payment)) {
+            throw new IllegalArgumentException("결제 금액이 수강료와 일치하지 않습니다.");
+        }
+    }
+
+    @Override
+    protected void validateCapacity(int currentCount) {
+        if (capacity.isOver(currentCount)) {
+            throw new IllegalStateException(String.format("수강 인원이 초과되었습니다. (최대: %d명)", capacity.getValue()));
+        }
+    }
+}
diff --git a/src/test/java/nextstep/courses/domain/PaidEnrollmentPolicyTest.java b/src/test/java/nextstep/courses/domain/PaidEnrollmentPolicyTest.java
new file mode 100644
index 000000000..a3554f638
--- /dev/null
+++ b/src/test/java/nextstep/courses/domain/PaidEnrollmentPolicyTest.java
@@ -0,0 +1,43 @@
+package nextstep.courses.domain;
+
+import static org.assertj.core.api.Assertions.*;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.DisplayNameGeneration;
+import org.junit.jupiter.api.DisplayNameGenerator;
+import org.junit.jupiter.api.Test;
+
+@DisplayNameGeneration(DisplayNameGenerator.ReplaceUnderscores.class)
+class PaidEnrollmentPolicyTest {
+
+    private PaidEnrollmentPolicy policy;
+
+    @BeforeEach
+    void setUp() {
+        policy = new PaidEnrollmentPolicy(3, 50000);
+    }
+
+    @Test
+    void validate_정상입력_성공() {
+        assertThatCode(() -> policy.validate(new Money(50000), 0)).doesNotThrowAnyException();
+    }
+
+    @Test
+    void validate_결제금액불일치_예외발생() {
+        assertThatThrownBy(() -> policy.validate(new Money(30000), 0))
+                .isInstanceOf(IllegalArgumentException.class)
+                .hasMessageContaining("결제 금액이 수강료와 일치하지 않습니다");
+    }
+
+    @Test
+    void validate_인원초과_예외발생() {
+        assertThatThrownBy(() -> policy.validate(new Money(50000), 3))
+                .isInstanceOf(IllegalStateException.class)
+                .hasMessageContaining("수강 인원이 초과");
+    }
+
+    @Test
+    void getType_PAID반환() {
+        assertThat(policy.getType()).isEqualTo(SessionType.PAID);
+    }
+}

From c2844b4ec0ef784530e927b930ed5a0454467a5f Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Thu, 11 Dec 2025 08:06:24 +0900
Subject: [PATCH 44/45] =?UTF-8?q?refactor:=20Session=20=EA=B5=AC=EC=A1=B0?=
 =?UTF-8?q?=20=EB=8B=A8=EC=88=9C=ED=99=94=20=EB=B0=8F=20=EC=A0=95=EC=B1=85?=
 =?UTF-8?q?=20=EA=B8=B0=EB=B0=98=20=EA=B5=AC=EC=84=B1=EC=9C=BC=EB=A1=9C=20?=
 =?UTF-8?q?=ED=86=B5=ED=95=A9?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

FreeSession.java / PaidSession.java
- Session 하위 구현 제거
- 정책 기반 구조로 대체됨에 따라 클래스 삭제

Session.java
- 추상 클래스 → 단일 클래스로 변경
- EnrollmentPolicy 의존성 추가하여 결제·정원 검증을 정책에 위임
- enroll 로직에서 상태 검증 후 정책 검증 호출하도록 통합
- getType() 추가하여 세션 타입 조회 가능

PaidSessionTest.java
- 정책 기반 구조로 변경됨에 따라 기존 PaidSession 테스트 삭제

SessionTest.java
- FreeSessionTest → SessionTest로 변경
- Session + FreeEnrollmentPolicy 조합으로 생성/수강 신청 테스트하도록 수정
- 모집 상태 검증 로직 유지
---
 .../nextstep/courses/domain/FreeSession.java  | 17 ----
 .../nextstep/courses/domain/PaidSession.java  | 35 ---------
 .../java/nextstep/courses/domain/Session.java | 32 ++++----
 .../courses/domain/PaidSessionTest.java       | 78 -------------------
 ...{FreeSessionTest.java => SessionTest.java} | 12 +--
 5 files changed, 26 insertions(+), 148 deletions(-)
 delete mode 100644 src/main/java/nextstep/courses/domain/FreeSession.java
 delete mode 100644 src/main/java/nextstep/courses/domain/PaidSession.java
 delete mode 100644 src/test/java/nextstep/courses/domain/PaidSessionTest.java
 rename src/test/java/nextstep/courses/domain/{FreeSessionTest.java => SessionTest.java} (77%)

diff --git a/src/main/java/nextstep/courses/domain/FreeSession.java b/src/main/java/nextstep/courses/domain/FreeSession.java
deleted file mode 100644
index d8753d33a..000000000
--- a/src/main/java/nextstep/courses/domain/FreeSession.java
+++ /dev/null
@@ -1,17 +0,0 @@
-package nextstep.courses.domain;
-
-public class FreeSession extends Session {
-    public FreeSession(CoverImage coverImage, SessionPeriod period) {
-        super(coverImage, period);
-    }
-
-    public FreeSession(CoverImage coverImage, SessionPeriod period, SessionStatus status) {
-        super(coverImage, period, status);
-    }
-
-    @Override
-    protected void validatePaymentPolicy(Money payment) {}
-
-    @Override
-    protected void validateCapacityPolicy() {}
-}
diff --git a/src/main/java/nextstep/courses/domain/PaidSession.java b/src/main/java/nextstep/courses/domain/PaidSession.java
deleted file mode 100644
index 891bb8b00..000000000
--- a/src/main/java/nextstep/courses/domain/PaidSession.java
+++ /dev/null
@@ -1,35 +0,0 @@
-package nextstep.courses.domain;
-
-public class PaidSession extends Session {
-    private final Capacity capacity;
-    private final Money price;
-
-    public PaidSession(CoverImage coverImage, SessionPeriod period, int capacity, int price) {
-        this(coverImage, period, SessionStatus.PREPARING, new Capacity(capacity), new Money(price));
-    }
-
-    public PaidSession(CoverImage coverImage, SessionPeriod period, SessionStatus status, int capacity, int price) {
-        this(coverImage, period, status, new Capacity(capacity), new Money(price));
-    }
-
-    public PaidSession(
-            CoverImage coverImage, SessionPeriod period, SessionStatus status, Capacity capacity, Money price) {
-        super(coverImage, period, status);
-        this.capacity = capacity;
-        this.price = price;
-    }
-
-    @Override
-    protected void validatePaymentPolicy(Money payment) {
-        if (!price.isSameAs(payment)) {
-            throw new IllegalArgumentException("결제 금액이 수강료와 일치하지 않습니다.");
-        }
-    }
-
-    @Override
-    protected void validateCapacityPolicy() {
-        if (this.capacity.isOver(enrollmentCount())) {
-            throw new IllegalStateException(String.format("수강 인원이 초과되었습니다. (최대: %d명)", capacity.getValue()));
-        }
-    }
-}
diff --git a/src/main/java/nextstep/courses/domain/Session.java b/src/main/java/nextstep/courses/domain/Session.java
index dfa148956..eafaaa950 100644
--- a/src/main/java/nextstep/courses/domain/Session.java
+++ b/src/main/java/nextstep/courses/domain/Session.java
@@ -1,46 +1,48 @@
 package nextstep.courses.domain;
 
-public abstract class Session {
+public class Session {
     private final Long id;
     private final CoverImage coverImage;
     private final SessionPeriod period;
     private final SessionStatus status;
+    private final EnrollmentPolicy enrollmentPolicy;
     private final Enrollments enrollments;
 
-    public Session(CoverImage coverImage, SessionPeriod period) {
-        this(0L, coverImage, period, SessionStatus.PREPARING, new Enrollments());
+    public Session(CoverImage coverImage, SessionPeriod period, EnrollmentPolicy policy) {
+        this(0L, coverImage, period, SessionStatus.PREPARING, policy, new Enrollments());
     }
 
-    public Session(CoverImage coverImage, SessionPeriod period, SessionStatus status) {
-        this(0L, coverImage, period, status, new Enrollments());
+    public Session(CoverImage coverImage, SessionPeriod period, SessionStatus status, EnrollmentPolicy policy) {
+        this(0L, coverImage, period, status, policy, new Enrollments());
     }
 
     public Session(
-            Long id, CoverImage coverImage, SessionPeriod period, SessionStatus status, Enrollments enrollments) {
+            Long id,
+            CoverImage coverImage,
+            SessionPeriod period,
+            SessionStatus status,
+            EnrollmentPolicy policy,
+            Enrollments enrollments) {
         this.id = id;
         this.coverImage = coverImage;
         this.period = period;
         this.status = status;
+        this.enrollmentPolicy = policy;
         this.enrollments = enrollments;
     }
 
     public final void enroll(Enrollment enrollment, Money payment) {
         validateStatus();
-        validatePaymentPolicy(payment);
-        validateCapacityPolicy();
+        enrollmentPolicy.validate(payment, enrollmentCount());
         enrollments.add(enrollment);
     }
 
-    protected void validateStatus() {
+    private void validateStatus() {
         if (!status.canEnroll()) {
             throw new IllegalStateException(String.format("모집중인 강의만 수강 신청이 가능합니다. (현재 상태: %s)", status));
         }
     }
 
-    protected abstract void validatePaymentPolicy(Money payment);
-
-    protected abstract void validateCapacityPolicy();
-
     public int enrollmentCount() {
         return enrollments.count();
     }
@@ -48,4 +50,8 @@ public int enrollmentCount() {
     public SessionStatus getStatus() {
         return this.status;
     }
+
+    public SessionType getType() {
+        return enrollmentPolicy.getType();
+    }
 }
diff --git a/src/test/java/nextstep/courses/domain/PaidSessionTest.java b/src/test/java/nextstep/courses/domain/PaidSessionTest.java
deleted file mode 100644
index 4321181d0..000000000
--- a/src/test/java/nextstep/courses/domain/PaidSessionTest.java
+++ /dev/null
@@ -1,78 +0,0 @@
-package nextstep.courses.domain;
-
-import static org.assertj.core.api.Assertions.*;
-
-import java.time.LocalDate;
-import java.time.LocalDateTime;
-import org.junit.jupiter.api.BeforeEach;
-import org.junit.jupiter.api.DisplayNameGeneration;
-import org.junit.jupiter.api.DisplayNameGenerator;
-import org.junit.jupiter.api.Test;
-import org.junit.jupiter.params.ParameterizedTest;
-import org.junit.jupiter.params.provider.EnumSource;
-
-@DisplayNameGeneration(DisplayNameGenerator.ReplaceUnderscores.class)
-class PaidSessionTest {
-
-    private CoverImage coverImage;
-    private SessionPeriod period;
-
-    @BeforeEach
-    void setUp() {
-        coverImage = new CoverImage("image.png", 1024, 300, 200);
-        period = new SessionPeriod(LocalDate.of(2024, 1, 1), LocalDate.of(2024, 3, 31));
-    }
-
-    @Test
-    void 생성자_정상입력_생성성공() {
-        assertThat(new PaidSession(coverImage, period, 30, 50000).getStatus()).isEqualTo(SessionStatus.PREPARING);
-    }
-
-    @Test
-    void enroll_정상입력_성공() {
-        PaidSession session = new PaidSession(coverImage, period, SessionStatus.RECRUITING, 3, 50000);
-        Enrollment enrollment = new Enrollment(1L, 1L, LocalDateTime.now());
-
-        session.enroll(enrollment, new Money(50000));
-
-        assertThat(session.enrollmentCount()).isEqualTo(1);
-    }
-
-    @Test
-    void enroll_결제금액불일치_예외발생() {
-        PaidSession session = new PaidSession(coverImage, period, SessionStatus.RECRUITING, 3, 50000);
-        Enrollment enrollment = new Enrollment(1L, 1L, LocalDateTime.now());
-        Money wrongPayment = new Money(30000);
-
-        assertThatThrownBy(() -> session.enroll(enrollment, wrongPayment))
-                .isInstanceOf(IllegalArgumentException.class)
-                .hasMessageContaining("결제 금액이 수강료와 일치하지 않습니다");
-    }
-
-    @Test
-    void enroll_인원초과_예외발생() {
-        PaidSession session = new PaidSession(coverImage, period, SessionStatus.RECRUITING, 2, 50000);
-        Money payment = new Money(50000);
-
-        session.enroll(new Enrollment(1L, 1L, LocalDateTime.now()), payment);
-        session.enroll(new Enrollment(2L, 2L, LocalDateTime.now()), payment);
-
-        assertThatThrownBy(() -> session.enroll(new Enrollment(3L, 3L, LocalDateTime.now()), payment))
-                .isInstanceOf(IllegalStateException.class)
-                .hasMessageContaining("수강 인원이 초과");
-    }
-
-    @ParameterizedTest(name = "상태:{0}")
-    @EnumSource(
-            value = SessionStatus.class,
-            names = {"PREPARING", "CLOSED"})
-    void enroll_모집중이아닐시_예외발생(SessionStatus status) {
-        PaidSession session = new PaidSession(coverImage, period, status, 2, 50000);
-
-        Enrollment enrollment = new Enrollment(1L, 1L, LocalDateTime.now());
-
-        assertThatThrownBy(() -> session.enroll(enrollment, Money.ZERO))
-                .isInstanceOf(IllegalStateException.class)
-                .hasMessageContaining("모집중인 강의만");
-    }
-}
diff --git a/src/test/java/nextstep/courses/domain/FreeSessionTest.java b/src/test/java/nextstep/courses/domain/SessionTest.java
similarity index 77%
rename from src/test/java/nextstep/courses/domain/FreeSessionTest.java
rename to src/test/java/nextstep/courses/domain/SessionTest.java
index 6cc611b28..9cd1ae187 100644
--- a/src/test/java/nextstep/courses/domain/FreeSessionTest.java
+++ b/src/test/java/nextstep/courses/domain/SessionTest.java
@@ -12,8 +12,7 @@
 import org.junit.jupiter.params.provider.EnumSource;
 
 @DisplayNameGeneration(DisplayNameGenerator.ReplaceUnderscores.class)
-class FreeSessionTest {
-
+class SessionTest {
     private CoverImage coverImage;
     private SessionPeriod period;
 
@@ -25,12 +24,15 @@ void setUp() {
 
     @Test
     void 생성자_정상입력_생성성공() {
-        assertThat(new FreeSession(coverImage, period).getStatus()).isEqualTo(SessionStatus.PREPARING);
+        Session session = new Session(coverImage, period, new FreeEnrollmentPolicy());
+
+        assertThat(session.getStatus()).isEqualTo(SessionStatus.PREPARING);
+        assertThat(session.getType()).isEqualTo(SessionType.FREE);
     }
 
     @Test
     void enroll_모집중_성공() {
-        Session session = new FreeSession(coverImage, period, SessionStatus.RECRUITING);
+        Session session = new Session(coverImage, period, SessionStatus.RECRUITING, new FreeEnrollmentPolicy());
         Enrollment enrollment = new Enrollment(1L, 1L, LocalDateTime.now());
 
         session.enroll(enrollment, Money.ZERO);
@@ -43,7 +45,7 @@ void setUp() {
             value = SessionStatus.class,
             names = {"PREPARING", "CLOSED"})
     void enroll_모집중이아닐시_예외발생(SessionStatus status) {
-        FreeSession session = new FreeSession(coverImage, period, status);
+        Session session = new Session(coverImage, period, status, new FreeEnrollmentPolicy());
 
         Enrollment enrollment = new Enrollment(1L, 1L, LocalDateTime.now());
 

From a0cd14a716cab4b13c62e96716a9b81e0dbe86cc Mon Sep 17 00:00:00 2001
From: ghtjr410 <ghtjr410@gmail.com>
Date: Thu, 11 Dec 2025 08:21:07 +0900
Subject: [PATCH 45/45] =?UTF-8?q?docs:=20=EC=A0=95=EC=B1=85=20=EA=B8=B0?=
 =?UTF-8?q?=EB=B0=98=20Session=20=EA=B5=AC=EC=A1=B0=EB=A1=9C=20=EB=AC=B8?=
 =?UTF-8?q?=EC=84=9C=20=EB=82=B4=EC=9A=A9=20=EC=97=85=EB=8D=B0=EC=9D=B4?=
 =?UTF-8?q?=ED=8A=B8?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

02-lms-domain-model.md
- Session을 추상 클래스 기반 → 정책 위임 방식으로 변경
- EnrollmentPolicy 중심 구조(템플릿 메서드) 설명 추가
- Free/Paid 정책의 역할 및 검증 규칙 명확히 정리
- Session 타입 조회가 Policy 반환값 기반임을 명시
---
 docs/02-lms-domain-model.md | 36 +++++++++++++++++++++---------------
 1 file changed, 21 insertions(+), 15 deletions(-)

diff --git a/docs/02-lms-domain-model.md b/docs/02-lms-domain-model.md
index fd98f596a..a8543f3e3 100644
--- a/docs/02-lms-domain-model.md
+++ b/docs/02-lms-domain-model.md
@@ -43,24 +43,30 @@
 - [x] 강의 추가
 - [x] 강의 개수 조회
 
-#### Session (추상 클래스, 템플릿 메서드 패턴 적용)
-- [x] 수강 신청 – 템플릿 메서드 방식
-  - [x] `final` enroll(enrollment, payment) 정의 
+#### Session
+- [x] 수강 신청
   - [x] 모집중 상태 검증
-  - [x] 결제 정책 검증 – 하위에서 구현 (validatePaymentPolicy)
-  - [x] 정원 정책 검증 – 하위에서 구현 (validateCapacityPolicy)
+  - [x] Policy에 검증 위임
 - [x] 수강 인원 조회
+- [x] 강의 타입 조회 (Policy에서 반환)
 
-#### FreeSession
-- [x] Session 상속
-- [x] 수강 신청
-  - [x] 결제 정책 없음 → validatePaymentPolicy(): 빈 구현
-  - [x] 정원 정책 없음 → validateCapacityPolicy(): 빈 구현
-#### PaidSession
-- [x] Session 상속
-- [x] 수강 신청
-  - [x] 결제 금액 검증
-  - [x] 수강 인원 검증
+#### EnrollmentPolicy (추상 클래스, 템플릿 메서드 패턴)
+- [x] final validate(payment, currentCount) - 알고리즘 순서 강제
+- [x] 결제 검증 (validatePayment) - 하위에서 구현
+- [x] 정원 검증 (validateCapacity) - 하위에서 구현
+- [x] 강의 타입 반환 (getType) - 하위에서 구현
+
+#### FreeEnrollmentPolicy
+- [x] EnrollmentPolicy 상속
+- [x] 결제 검증: 빈 구현 (무료)
+- [x] 정원 검증: 빈 구현 (제한 없음)
+- [x] 타입 반환: FREE
+
+#### PaidEnrollmentPolicy
+- [x] EnrollmentPolicy 상속
+- [x] 결제 금액 검증 (수강료 일치)
+- [x] 수강 인원 검증 (정원 초과)
+- [x] 타입 반환: PAID
 
 #### Enrollments (일급 컬렉션)
 - [x] 수강 신청 추가