From c531df424c861695296f8e837269ff6332815ed7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=A1chym=20Metli=C4=8Dka?= <metlicka@2n.com>
Date: Sun, 15 Feb 2026 09:40:27 +0100
Subject: [PATCH] refactor: replace Collectors.toMap with custom collector for
 case-insensitive file name ordering to simplify lookup in the table while
 debugging tests.

---
 .../org/openapitools/codegen/TestUtils.java   | 27 +++++-
 .../codegen/config/MergedSpecBuilderTest.java |  5 +-
 .../codegen/java/JavaClientCodegenTest.java   | 53 +++++------
 .../JavaValidationArrayPrimitivesTest.java    | 10 +-
 .../JavaJAXRSCXFCDIServerCodegenTest.java     |  6 +-
 .../jaxrs/JavaJAXRSSpecServerCodegenTest.java | 14 ++-
 .../codegen/java/jaxrs/JavaJaxrsBaseTest.java |  7 +-
 ...vaJaxrsResteasyServerCodegenModelTest.java |  5 +-
 .../jaxrs/JavaJerseyServerCodegenTest.java    |  3 +-
 .../JavaMicroprofileServerCodegenTest.java    | 19 ++--
 .../java/spring/SpringCodegenTest.java        | 95 +++++++++----------
 .../spring/KotlinSpringServerCodegenTest.java |  9 +-
 .../codegen/php/PhpClientCodegenTest.java     |  7 +-
 .../php/PhpNextgenClientCodegenTest.java      |  9 +-
 14 files changed, 139 insertions(+), 130 deletions(-)

diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/TestUtils.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/TestUtils.java
index b0b0396a2ab9..b8b1f1cdd5d1 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/TestUtils.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/TestUtils.java
@@ -15,6 +15,7 @@
 import io.swagger.v3.oas.models.media.Schema;
 import io.swagger.v3.oas.models.servers.Server;
 import io.swagger.v3.parser.core.models.ParseOptions;
+import org.jetbrains.annotations.NotNull;
 import org.openapitools.codegen.java.assertions.JavaFileAssert;
 import org.openapitools.codegen.model.ModelMap;
 import org.openapitools.codegen.model.ModelsMap;
@@ -24,12 +25,12 @@
 import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.List;
-import java.util.Map;
+import java.util.*;
+import java.util.function.Function;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
+import java.util.stream.Collector;
+import java.util.stream.Collectors;
 
 import static org.testng.Assert.*;
 
@@ -352,4 +353,22 @@ public static Path newTempFolder() {
 
         return tempDir;
     }
+
+
+    /**
+     * Returns a collector that collects files into a {@link TreeMap} sorted by file name,
+     * using case-insensitive ordering (but accepting both keys - e.g. "application" and "Application").
+     * This is used to have files sorted by name (case-insensitive) to simplify lookup during test debugging.
+     */
+    @NotNull
+    public static Collector<File, ?, TreeMap<String, File>> collectToCaseInsensitiveOrderedCaseSensitiveKeyMap() {
+        return Collectors.toMap(
+                File::getName,
+                Function.identity(),
+                (existing, replacement) -> {
+                    throw new IllegalStateException("Duplicate key: " + existing);
+                },
+                () -> new TreeMap<>(Comparator.<String, String>comparing(s -> s.toLowerCase(Locale.ROOT))
+                        .thenComparing(Comparator.naturalOrder())));
+    }
 }
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/config/MergedSpecBuilderTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/config/MergedSpecBuilderTest.java
index 42f9e0a547d1..59d572e0f6db 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/config/MergedSpecBuilderTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/config/MergedSpecBuilderTest.java
@@ -15,9 +15,8 @@
 import java.nio.file.Files;
 import java.nio.file.Paths;
 import java.util.Map;
-import java.util.function.Function;
-import java.util.stream.Collectors;
 
+import static org.openapitools.codegen.TestUtils.collectToCaseInsensitiveOrderedCaseSensitiveKeyMap;
 import static org.openapitools.codegen.languages.SpringCodegen.*;
 
 public class MergedSpecBuilderTest {
@@ -66,7 +65,7 @@ private void assertFilesFromMergedSpec(String mergedSpec) throws IOException {
 
         DefaultGenerator generator = new DefaultGenerator();
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("Spec1Api.java"))
                 .assertMethod("spec1Operation").hasReturnType("ResponseEntity<Spec1Model>")
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/JavaClientCodegenTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/JavaClientCodegenTest.java
index 94a0a6f4535e..d882941fb7db 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/JavaClientCodegenTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/JavaClientCodegenTest.java
@@ -58,7 +58,6 @@
 import java.nio.file.Paths;
 import java.util.*;
 import java.util.function.Consumer;
-import java.util.function.Function;
 import java.util.function.Predicate;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
@@ -1160,7 +1159,7 @@ public void shouldGenerateBlockingAndNoBlockingOperationsForWebClient() {
 
         DefaultGenerator generator = new DefaultGenerator();
         Map<String, File> files = generator.opts(configurator.toClientOptInput()).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("StoreApi.java"))
                 .assertMethod("getInventory")
@@ -1579,7 +1578,7 @@ public void testMicroprofileGenerateCorrectJsonbCreator_issue12622() {
                 .setOutputDir(output.toString().replace("\\", "/"));
 
         Map<String, File> files = new DefaultGenerator().opts(configurator.toClientOptInput()).generate()
-                .stream().collect(Collectors.toMap(File::getName, Function.identity()));
+                .stream().collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("Foo.java"))
                 .assertConstructor("String", "Integer")
@@ -1613,7 +1612,7 @@ public void testMicroprofileGenerateCorrectJacksonGenerator_issue18336() throws
         final ClientOptInput clientOptInput = configurator.toClientOptInput();
         DefaultGenerator generator = new DefaultGenerator();
         Map<String, File> files = generator.opts(clientOptInput).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("Pet.java"))
                 .assertConstructor("String")
@@ -1636,7 +1635,7 @@ public void testJavaClientDefaultValues_issueNoNumber() {
                 .setInputSpec("src/test/resources/bugs/java-codegen-empty-array-as-default-value/issue_wrong-default.yaml");
 
         Map<String, File> files = new DefaultGenerator().opts(configurator.toClientOptInput()).generate()
-                .stream().collect(Collectors.toMap(File::getName, Function.identity()));
+                .stream().collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("DefaultValuesType.java"))
                 .assertProperty("stringDefault")
@@ -1660,7 +1659,7 @@ public void testWebClientJsonCreatorWithNullable_issue12790() {
                 .setOutputDir(output.toString().replace("\\", "/"));
 
         Map<String, File> files = new DefaultGenerator().opts(configurator.toClientOptInput()).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("TestObject.java"))
                 .printFileContent()
@@ -1727,7 +1726,7 @@ public void testReferencedHeader2() {
                 .setOutputDir(output.toString().replace("\\", "/"));
 
         Map<String, File> files = new DefaultGenerator().opts(configurator.toClientOptInput()).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("DefaultApi.java"))
                 .assertMethod("operationWithHttpInfo")
@@ -2044,7 +2043,7 @@ private static Map<String, File> generateFromContract(
                 .setOutputDir(output.toString());
         consumer.accept(configurator);
         return new DefaultGenerator().opts(configurator.toClientOptInput()).generate()
-                .stream().collect(Collectors.toMap(File::getName, Function.identity()));
+                .stream().collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
     }
 
     @Test
@@ -2200,7 +2199,7 @@ public void shouldNotAddAdditionalModelAnnotationsToAbstractOpenApiSchema_issue1
                 .setOutputDir(output.toString().replace("\\", "/"));
 
         Map<String, File> files = new DefaultGenerator().opts(configurator.toClientOptInput()).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("AbstractOpenApiSchema.java"))
                 .assertTypeAnnotations()
@@ -2371,7 +2370,7 @@ public void testEnumCaseInsensitive_issue8084() {
         codegen.additionalProperties().put(USE_ENUM_CASE_INSENSITIVE, "true");
 
         Map<String, File> files = new DefaultGenerator().opts(new ClientOptInput().openAPI(openAPI).config(codegen))
-                .generate().stream().collect(Collectors.toMap(File::getName, Function.identity()));
+                .generate().stream().collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("EnumTest.java"))
                 .assertMethod("fromValue")
@@ -2387,7 +2386,7 @@ public void testEnumCaseSensitive_issue8084() {
         codegen.additionalProperties().put(USE_ENUM_CASE_INSENSITIVE, "false");
 
         Map<String, File> files = new DefaultGenerator().opts(new ClientOptInput().openAPI(openAPI).config(codegen))
-                .generate().stream().collect(Collectors.toMap(File::getName, Function.identity()));
+                .generate().stream().collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("EnumTest.java"))
                 .assertMethod("fromValue")
@@ -2402,7 +2401,7 @@ public void testMapOfInnerEnum_issue19393() {
         codegen.setOutputDir(newTempFolder().toString());
 
         Map<String, File> files = new DefaultGenerator().opts(new ClientOptInput().openAPI(openAPI).config(codegen))
-                .generate().stream().collect(Collectors.toMap(File::getName, Function.identity()));
+                .generate().stream().collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("EmployeeWithMapOfEnum.java"))
                 .assertProperty("projectRole")
@@ -2444,7 +2443,7 @@ public void testHandleConstantParams() {
         codegen.setAutosetConstants(true);
 
         Map<String, File> files = new DefaultGenerator().opts(new ClientOptInput().openAPI(openAPI).config(codegen))
-                .generate().stream().collect(Collectors.toMap(File::getName, Function.identity()));
+                .generate().stream().collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         File apiFile = files.get("HelloExampleApi.java");
         Assertions.assertNotNull(apiFile);
@@ -2462,7 +2461,7 @@ public void testAllOfWithSinglePrimitiveTypeRef() {
         codegen.setAutosetConstants(true);
 
         Map<String, File> files = new DefaultGenerator().opts(new ClientOptInput().openAPI(openAPI).config(codegen))
-                .generate().stream().collect(Collectors.toMap(File::getName, Function.identity()));
+                .generate().stream().collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         assertNull(files.get("AllOfDatetime.java"));
     }
@@ -2478,7 +2477,7 @@ public void testOpenapiGeneratorIgnoreListOption() {
         codegen.openapiGeneratorIgnoreList().add("pom.xml");
 
         Map<String, File> files = new DefaultGenerator().opts(new ClientOptInput().openAPI(openAPI).config(codegen))
-                .generate().stream().collect(Collectors.toMap(File::getName, Function.identity()));
+                .generate().stream().collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         // make sure README.md and pom.xml are not generated
         assertNull(files.get("README.md"));
@@ -2494,7 +2493,7 @@ public void testEnumDiscriminatorDefaultValueIsNotString() {
         codegen.setOutputDir(output.toString());
 
         Map<String, File> files = new DefaultGenerator().opts(new ClientOptInput().openAPI(openAPI).config(codegen))
-                .generate().stream().collect(Collectors.toMap(File::getName, Function.identity()));
+                .generate().stream().collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         Map<String, String> expectedContents = Map.of(
                 "Cat", "this.petType = PetTypeEnum.CATTY",
@@ -2579,7 +2578,7 @@ private void testHandleURIEnum(String library, String[] expectedInnerEnumLines,
                 .setOutputDir(output.toString().replace("\\", "/"));
 
         Map<String, File> files = new DefaultGenerator().opts(configurator.toClientOptInput()).generate()
-                .stream().collect(Collectors.toMap(File::getName, Function.identity()));
+                .stream().collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         // enum
         File modelFile = files.get("Metadata.java");
@@ -2756,7 +2755,7 @@ public void testRestClientJsonCreatorWithNullable_issue12790() {
                 .setOutputDir(output.toString().replace("\\", "/"));
 
         Map<String, File> files = new DefaultGenerator().opts(configurator.toClientOptInput()).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("TestObject.java"))
                 .printFileContent()
@@ -3241,7 +3240,7 @@ public void testRestTemplateWithCustomUserAgent() {
                 .setOutputDir(output.toString().replace("\\", "/"));
 
         final Map<String, File> files = new DefaultGenerator().opts(configurator.toClientOptInput()).generate()
-                .stream().collect(Collectors.toMap(File::getName, Function.identity()));
+                .stream().collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         final JavaFileAssert apiClient = JavaFileAssert.assertThat(files.get("ApiClient.java"))
                 .printFileContent();
@@ -3531,7 +3530,7 @@ public void callNativeServiceWithEmptyResponseSync() throws IOException {
         DefaultGenerator generator = new DefaultGenerator();
 
         Map<String, File> files = generator.opts(clientOptInput).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         File apiFile = files.get("DefaultApi.java");
         assertNotNull(apiFile);
@@ -3563,7 +3562,7 @@ public void annotationLibraryDoesNotCauseImportConflicts() throws IOException {
         DefaultGenerator generator = new DefaultGenerator();
 
         Map<String, File> files = generator.opts(clientOptInput).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         File apiFile = files.get("Schema.java");
         assertNotNull(apiFile);
@@ -3592,7 +3591,7 @@ public void annotationLibraryGeneratesCorrectImports() throws IOException {
         DefaultGenerator generator = new DefaultGenerator();
 
         Map<String, File> files = generator.opts(clientOptInput).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         File apiFile = files.get("Schema.java");
         assertNotNull(apiFile);
@@ -3627,7 +3626,7 @@ public void callNativeServiceWithEmptyResponseAsync() throws IOException {
         DefaultGenerator generator = new DefaultGenerator();
 
         Map<String, File> files = generator.opts(clientOptInput).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         File apiFile = files.get("DefaultApi.java");
         assertNotNull(apiFile);
@@ -3648,7 +3647,7 @@ public void testEnumWithImplements() {
         codegen.setOutputDir(output.toString());
 
         Map<String, File> files = new DefaultGenerator().opts(new ClientOptInput().openAPI(openAPI).config(codegen))
-                .generate().stream().collect(Collectors.toMap(File::getName, Function.identity()));
+                .generate().stream().collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("Type.java")).fileContains("Type implements java.io.Serializable {");
     }
@@ -3672,7 +3671,7 @@ public void testClassesAreValidJavaJersey2() {
                 .setOutputDir(output.toString().replace("\\", "/"));
 
         Map<String, File> files = new DefaultGenerator().opts(configurator.toClientOptInput()).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         File oneOfFile = files.get("ResultObjectOneOf.java");
         assertNotNull(oneOfFile);
@@ -3709,7 +3708,7 @@ public void testClassesAreValidJavaJersey3() {
                 .setOutputDir(output.toString().replace("\\", "/"));
 
         Map<String, File> files = new DefaultGenerator().opts(configurator.toClientOptInput()).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         File oneOfFile = files.get("ResultObjectOneOf.java");
         assertNotNull(oneOfFile);
@@ -3746,7 +3745,7 @@ public void testClassesAreValidJavaOkHttpGson() {
                 .setOutputDir(output.toString().replace("\\", "/"));
 
         Map<String, File> files = new DefaultGenerator().opts(configurator.toClientOptInput()).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         File oneOfFile = files.get("ResultObjectOneOf.java");
         assertNotNull(oneOfFile);
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/JavaValidationArrayPrimitivesTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/JavaValidationArrayPrimitivesTest.java
index 322c36f8bd7d..57ed76216b5b 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/JavaValidationArrayPrimitivesTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/JavaValidationArrayPrimitivesTest.java
@@ -34,8 +34,8 @@
 import java.util.Collections;
 import java.util.Map;
 import java.util.function.Consumer;
-import java.util.function.Function;
-import java.util.stream.Collectors;
+
+import static org.openapitools.codegen.TestUtils.collectToCaseInsensitiveOrderedCaseSensitiveKeyMap;
 
 public class JavaValidationArrayPrimitivesTest {
     private static Consumer<Map<String, File>> assertWithValidationWithoutJsonNullable() {
@@ -225,7 +225,7 @@ public void shouldAddValidAnnotationIntoCollectionWhenBeanValidationIsEnabled_is
 
         final DefaultGenerator generator = new DefaultGenerator();
         final Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         asserts.accept(files);
     }
@@ -408,7 +408,7 @@ public void shouldNotAddValidAnnotationIntoCollectionWhenBeanValidationIsNotEnab
 
         final DefaultGenerator generator = new DefaultGenerator();
         final Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         asserts.accept(files);
     }
@@ -445,7 +445,7 @@ public void typeMappingsForCollections(Map<String, String> typeMappings, String
         input.config(codegen);
         final DefaultGenerator generator = new DefaultGenerator();
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         String arrayMapping = typeMappings.getOrDefault("array", "List");
         // @Valid@Size(min = 5) is not nice, but not related to this fix
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/jaxrs/JavaJAXRSCXFCDIServerCodegenTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/jaxrs/JavaJAXRSCXFCDIServerCodegenTest.java
index 33731edb6520..2d3a9d388693 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/jaxrs/JavaJAXRSCXFCDIServerCodegenTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/jaxrs/JavaJAXRSCXFCDIServerCodegenTest.java
@@ -15,8 +15,8 @@
 import java.io.File;
 import java.nio.file.Files;
 import java.util.Map;
-import java.util.function.Function;
-import java.util.stream.Collectors;
+
+import static org.openapitools.codegen.TestUtils.collectToCaseInsensitiveOrderedCaseSensitiveKeyMap;
 
 public class JavaJAXRSCXFCDIServerCodegenTest extends JavaJaxrsBaseTest {
 
@@ -42,7 +42,7 @@ public void testHandleDefaultValue_issue8535() throws Exception {
 
         DefaultGenerator generator = new DefaultGenerator();
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("TestHeadersApi.java"))
                 .assertMethod("headersTest")
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/jaxrs/JavaJAXRSSpecServerCodegenTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/jaxrs/JavaJAXRSSpecServerCodegenTest.java
index 2e9e2e2153d2..45f4f21cb7c9 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/jaxrs/JavaJAXRSSpecServerCodegenTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/jaxrs/JavaJAXRSSpecServerCodegenTest.java
@@ -25,8 +25,6 @@
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
-import java.util.function.Function;
-import java.util.stream.Collectors;
 
 import static org.openapitools.codegen.TestUtils.*;
 import static org.openapitools.codegen.languages.JavaJAXRSSpecServerCodegen.*;
@@ -676,7 +674,7 @@ public void testHandleDefaultValue_issue8535() throws Exception {
 
         DefaultGenerator generator = new DefaultGenerator();
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("TestHeadersApi.java"))
                 .assertMethod("headersTest")
@@ -747,7 +745,7 @@ public void testValidAnnotation_issue14432() throws Exception {
 
         DefaultGenerator generator = new DefaultGenerator();
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("ComplexObject.java"))
                 .fileContains("private @Valid List<LocalDate> dates")
@@ -938,7 +936,7 @@ public void testHandleRequiredAndReadOnlyPropertiesCorrectly() throws Exception
 
         DefaultGenerator generator = new DefaultGenerator();
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("ReadonlyAndRequiredProperties.java"))
                 .assertProperty("requiredYesReadonlyYes")
@@ -1185,7 +1183,7 @@ public void testEnumUnknownDefaultCaseDeserializationTrue_issue13444() throws Ex
 
         DefaultGenerator generator = new DefaultGenerator();
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("Color.java"))
                 .assertMethod("fromValue").bodyContainsLines("return UNKNOWN_DEFAULT_OPEN_API");
@@ -1208,7 +1206,7 @@ public void testEnumUnknownDefaultCaseDeserializationNotSet_issue13444() throws
 
         DefaultGenerator generator = new DefaultGenerator();
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("Color.java"))
                 .assertMethod("fromValue").bodyContainsLines("throw new IllegalArgumentException(\"Unexpected value '\" + value + \"'\");");
@@ -1232,7 +1230,7 @@ public void disableGenerateJsonCreator() throws Exception {
 
         DefaultGenerator generator = new DefaultGenerator();
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         assertFileNotContains(files.get("RequiredProperties.java").toPath(), "@JsonCreator");
     }
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/jaxrs/JavaJaxrsBaseTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/jaxrs/JavaJaxrsBaseTest.java
index e1e77d5a53f8..4dfcd9b15669 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/jaxrs/JavaJaxrsBaseTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/jaxrs/JavaJaxrsBaseTest.java
@@ -17,11 +17,8 @@
 import java.nio.file.Paths;
 import java.util.List;
 import java.util.Map;
-import java.util.function.Function;
-import java.util.stream.Collectors;
 
-import static org.openapitools.codegen.TestUtils.assertFileContains;
-import static org.openapitools.codegen.TestUtils.assertFileNotContains;
+import static org.openapitools.codegen.TestUtils.*;
 import static org.openapitools.codegen.languages.AbstractJavaCodegen.JACKSON;
 
 public abstract class JavaJaxrsBaseTest {
@@ -318,7 +315,7 @@ public void testClassInheritanceEqualsHashCode() throws Exception {
         DefaultGenerator generator = new DefaultGenerator();
         Map<String, File> files = generator.opts(input)
                 .generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         // Assert that the base class does not call super.equals() or super.hashCode()
         JavaFileAssert.assertThat(files.get("BaseClass.java")).assertMethod("equals").bodyNotContainsLines("super");
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/jaxrs/JavaJaxrsResteasyServerCodegenModelTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/jaxrs/JavaJaxrsResteasyServerCodegenModelTest.java
index 66b9cd5e4734..66f4153bd9f4 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/jaxrs/JavaJaxrsResteasyServerCodegenModelTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/jaxrs/JavaJaxrsResteasyServerCodegenModelTest.java
@@ -18,9 +18,8 @@
 import java.io.File;
 import java.nio.file.Files;
 import java.util.Map;
-import java.util.function.Function;
-import java.util.stream.Collectors;
 
+import static org.openapitools.codegen.TestUtils.collectToCaseInsensitiveOrderedCaseSensitiveKeyMap;
 import static org.testng.Assert.assertEquals;
 import static org.testng.Assert.assertTrue;
 
@@ -86,7 +85,7 @@ public void testHandleDefaultValue_issue8535() throws Exception {
 
         DefaultGenerator generator = new DefaultGenerator();
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("TestHeadersApi.java"))
                 .assertMethod("headersTest")
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/jaxrs/JavaJerseyServerCodegenTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/jaxrs/JavaJerseyServerCodegenTest.java
index 8e4bc1c9f9d3..8300122d507c 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/jaxrs/JavaJerseyServerCodegenTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/jaxrs/JavaJerseyServerCodegenTest.java
@@ -29,6 +29,7 @@
 import java.util.stream.Collectors;
 
 import static org.openapitools.codegen.TestUtils.assertFileContains;
+import static org.openapitools.codegen.TestUtils.collectToCaseInsensitiveOrderedCaseSensitiveKeyMap;
 
 public class JavaJerseyServerCodegenTest extends JavaJaxrsBaseTest {
 
@@ -232,7 +233,7 @@ public void testHandleDefaultValue_issue8535() throws Exception {
 
         DefaultGenerator generator = new DefaultGenerator();
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("TestHeadersApi.java"))
                 .assertMethod("headersTest")
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/microprofile/JavaMicroprofileServerCodegenTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/microprofile/JavaMicroprofileServerCodegenTest.java
index 06cb837baa6d..369ebfa58623 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/microprofile/JavaMicroprofileServerCodegenTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/microprofile/JavaMicroprofileServerCodegenTest.java
@@ -16,9 +16,8 @@
 import java.nio.file.Files;
 import java.util.List;
 import java.util.Map;
-import java.util.function.Function;
-import java.util.stream.Collectors;
 
+import static org.openapitools.codegen.TestUtils.collectToCaseInsensitiveOrderedCaseSensitiveKeyMap;
 import static org.openapitools.codegen.TestUtils.validateJavaSourceFiles;
 
 public class JavaMicroprofileServerCodegenTest {
@@ -47,7 +46,7 @@ public void testEnumUnknownDefaultCaseDeserializationTrue_issue19674() throws Ex
 
         DefaultGenerator generator = new DefaultGenerator();
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("Color.java"))
                 .assertMethod("fromValue").bodyContainsLines("return UNKNOWN_DEFAULT_OPEN_API");
@@ -70,7 +69,7 @@ public void testEnumUnknownDefaultCaseDeserializationNotSet_issue19674() throws
 
         DefaultGenerator generator = new DefaultGenerator();
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("Color.java"))
                 .assertMethod("fromValue").bodyContainsLines("throw new IllegalArgumentException(\"Unexpected value '\" + text + \"'\");");
@@ -94,7 +93,7 @@ public void testMicroprofileCanHandleCookieParams() throws Exception {
         List<File> files = new DefaultGenerator().opts(input).generate();
 
         Map<String, File> filesMap = files.stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         validateJavaSourceFiles(files);
 
@@ -120,7 +119,7 @@ public void testMicroprofileCanHandleCookieParamsSingleRequest() throws Exceptio
         List<File> files = new DefaultGenerator().opts(input).generate();
 
         Map<String, File> filesMap = files.stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         validateJavaSourceFiles(files);
 
@@ -146,7 +145,7 @@ public void testGeneratedApiHasApiExceptionMapperRegisteredWhenUsingDefaultConfi
         List<File> files = new DefaultGenerator().opts(input).generate();
 
         Map<String, File> filesMap = files.stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         validateJavaSourceFiles(files);
 
@@ -174,7 +173,7 @@ public void testGeneratedApiDoesNotHaveApiExceptionMapperRegisteredWhenDisabling
         List<File> files = new DefaultGenerator().opts(input).generate();
 
         Map<String, File> filesMap = files.stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         validateJavaSourceFiles(files);
 
@@ -200,7 +199,7 @@ public void testGeneratedApiExceptionMapperHasProviderAnnotationWhenUsingDefault
         List<File> files = new DefaultGenerator().opts(input).generate();
 
         Map<String, File> filesMap = files.stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         validateJavaSourceFiles(files);
 
@@ -227,7 +226,7 @@ public void testGeneratedApiExceptionMapperDoesNotHaveProviderAnnotationWhenDisa
         List<File> files = new DefaultGenerator().opts(input).generate();
 
         Map<String, File> filesMap = files.stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         validateJavaSourceFiles(files);
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/spring/SpringCodegenTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/spring/SpringCodegenTest.java
index ac819033d71e..2f1d9d04a887 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/spring/SpringCodegenTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/spring/SpringCodegenTest.java
@@ -53,7 +53,6 @@
 import java.util.List;
 import java.util.Map;
 import java.util.function.Consumer;
-import java.util.function.Function;
 import java.util.stream.Collectors;
 
 import static java.util.stream.Collectors.groupingBy;
@@ -489,7 +488,7 @@ public void testJavaClientCorrectConstructorOrderForRequiredFields_issue15825()
         generator.setGenerateMetadata(false); // skip metadata and ↓ only generate models
         generator.setGeneratorPropertyDefault(CodegenConstants.MODELS, "true");
         Map<String, File> files = generator.opts(clientOptInput).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("SubType.java"))
                 .assertConstructor("TypeEnum", "SchemaVersion", "UUID", "Boolean", "Boolean", "SomeEnum")
@@ -888,7 +887,7 @@ public void shouldAddParameterWithInHeaderWhenImplicitHeadersIsTrue_issue14418()
         DefaultGenerator generator = new DefaultGenerator();
         generator.setGenerateMetadata(false);
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("TestApi.java"))
                 .isInterface()
@@ -925,7 +924,7 @@ public void shouldApiNameSuffixForApiClassname() throws IOException {
         DefaultGenerator generator = new DefaultGenerator();
         generator.setGenerateMetadata(false);
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("PetController.java"))
                 .isInterface();
@@ -959,7 +958,7 @@ public void shouldUseTagsForClassname() throws IOException {
         generator.setGenerateMetadata(false);
 
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("PetTagApi.java"))
                 .isInterface();
@@ -992,7 +991,7 @@ public void shouldNotUseTagsForClassname() throws IOException {
         DefaultGenerator generator = new DefaultGenerator();
         generator.setGenerateMetadata(false);
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("PetApi.java"))
                 .isInterface();
@@ -1024,7 +1023,7 @@ public void shouldAddValidAnnotationIntoCollectionWhenBeanValidationIsEnabled_is
         generator.setGenerateMetadata(false); // skip metadata and ↓ only generate models
         generator.setGeneratorPropertyDefault(CodegenConstants.MODELS, "true");
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("ResponseTest.java"))
                 .isNormalClass()
@@ -1084,7 +1083,7 @@ public void shouldAddValidAnnotationIntoCollectionWhenBeanValidationIsEnabled_is
         generator.setGenerateMetadata(false); // skip metadata and ↓ only generate models
         generator.setGeneratorPropertyDefault(CodegenConstants.MODELS, "true");
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("Foo.java"))
                 .isNormalClass()
@@ -1369,7 +1368,7 @@ private void beanValidationForFormatEmail(boolean useBeanValidation, boolean per
         generator.setGeneratorPropertyDefault(CodegenConstants.MODELS, "true");
 
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert javaFileAssert = JavaFileAssert.assertThat(files.get("PersonWithEmail.java"));
         if (useBeanValidation)
@@ -1481,7 +1480,7 @@ public void shouldGenerateValidCodeForReactiveControllerWithoutParams_issue14907
         generator.setGenerateMetadata(false); // skip metadata
 
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("ConsentControllerApi.java"))
                 .assertMethod("readAgreements", "ServerWebExchange");
@@ -1513,7 +1512,7 @@ public void shouldGenerateValidCodeWithPaginated_reactive_issue15265() throws IO
         generator.setGenerateMetadata(false); // skip metadata and ↓ only generate models
 
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("ConsentControllerApi.java"))
                 .assertMethod("paginated", "ServerWebExchange", "Pageable")
@@ -1546,7 +1545,7 @@ public void shouldGenerateValidCodeWithPaginated_nonReactive_issue15265() throws
         generator.setGenerateMetadata(false); // skip metadata and ↓ only generate models
 
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("ConsentControllerApi.java"))
                 .assertMethod("paginated", "Pageable")
@@ -2108,7 +2107,7 @@ public void shouldGenerateExternalDocs() throws IOException {
         generator.setGeneratorPropertyDefault(CodegenConstants.APIS, "true");
 
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("PetApi.java"))
                 .hasImports("io.swagger.v3.oas.annotations.ExternalDocumentation")
@@ -2546,7 +2545,7 @@ public void shouldGenerateBeanValidationOnHeaderParams() throws IOException {
         generator.setGenerateMetadata(false);
 
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("SomeMethodApi.java"))
                 .assertMethod("methodWithValidation")
@@ -2719,7 +2718,7 @@ public void shouldUseEqualsNullableForArrayWhenSetInConfig_issue13385() throws I
         generator.setGeneratorPropertyDefault(CodegenConstants.MODELS, "true");
 
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("TestObject.java"))
                 .assertMethod("equals")
@@ -2751,7 +2750,7 @@ public void shouldNotUseEqualsNullableForArrayWhenNotSetInConfig_issue13385() th
         generator.setGenerateMetadata(false); // skip metadata and ↓ only generate models
         generator.setGeneratorPropertyDefault(CodegenConstants.MODELS, "true");
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("TestObject.java"))
                 .assertMethod("equals")
@@ -2780,7 +2779,7 @@ public void useBeanValidationGenerateAnnotationsForRequestBody_issue13932() thro
         DefaultGenerator generator = new DefaultGenerator();
         generator.setGenerateMetadata(false);
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("AddApi.java"))
                 .assertMethod("addPost")
@@ -2811,7 +2810,7 @@ public void useBeanValidationGenerateAnnotationsForFormsRequestBody() throws IOE
         DefaultGenerator generator = new DefaultGenerator();
         generator.setGenerateMetadata(false);
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("AddApi.java"))
                 .assertMethod("addPost")
@@ -2851,7 +2850,7 @@ public void shouldHandleSeparatelyInterfaceAndModelAdditionalAnnotations() throw
         generator.setGenerateMetadata(false); // skip metadata and ↓ only generate models
         generator.setGeneratorPropertyDefault(CodegenConstants.MODELS, "true");
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("PatchRequestInner.java"))
                 .isInterface()
@@ -2898,7 +2897,7 @@ public void contractWithResolvedInnerEnumContainsEnumConverter() throws IOExcept
         generator.setGenerateMetadata(false);
 
         Map<String, File> files = generator.opts(clientOptInput).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("EnumConverterConfiguration.java"))
                 .assertMethod("ponyTypeConverter");
@@ -2977,7 +2976,7 @@ private Map<String, File> generateFromContract(String url, String library, Map<S
         generator.setGenerateMetadata(false);
 
         return generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
     }
 
     @Test
@@ -3035,7 +3034,7 @@ public void shouldGenerateJsonPropertyAnnotationLocatedInGetters_issue5705() thr
         generator.setGenerateMetadata(false); // skip metadata and ↓ only generate models
         generator.setGeneratorPropertyDefault(CodegenConstants.MODELS, "true");
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("ResponseObjectWithDifferentFieldNames.java"))
                 .assertProperty("normalPropertyName")
@@ -3103,7 +3102,7 @@ public void testReturnTypeVoidWithResponseEntity_issue12341() throws IOException
         generator.setGeneratorPropertyDefault(CodegenConstants.APIS, "true");
 
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert javaFileAssert = JavaFileAssert.assertThat(files.get("TestApi.java"));
         javaFileAssert
@@ -3148,7 +3147,7 @@ public void testReturnTypeVoidWithoutResponseEntityWithDelegate_issue12341() thr
         generator.setGeneratorPropertyDefault(CodegenConstants.APIS, "true");
 
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert javaFileAssert = JavaFileAssert.assertThat(files.get("TestApi.java"));
         javaFileAssert
@@ -3195,7 +3194,7 @@ public void testReturnTypeVoidWithoutResponseEntityWithoutDelegateWithAsync_issu
         generator.setGeneratorPropertyDefault(CodegenConstants.APIS, "true");
 
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert javaFileAssert = JavaFileAssert.assertThat(files.get("TestApi.java"));
         javaFileAssert
@@ -3234,7 +3233,7 @@ public void testReturnTypeVoidWithoutResponseEntityWithoutDelegateWithoutAsync_i
         generator.setGeneratorPropertyDefault(CodegenConstants.APIS, "true");
 
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert javaFileAssert = JavaFileAssert.assertThat(files.get("TestApi.java"));
         javaFileAssert
@@ -3273,7 +3272,7 @@ public void testHasRestControllerDoesNotHaveController_issue15264() throws IOExc
         generator.setGeneratorPropertyDefault(CodegenConstants.APIS, "true");
 
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert javaFileAssert = JavaFileAssert.assertThat(files.get("TestApi.java"));
         javaFileAssert
@@ -3311,7 +3310,7 @@ public void testDoesNotHasRestControllerHaveController_issue15264() throws IOExc
         generator.setGeneratorPropertyDefault(CodegenConstants.APIS, "true");
 
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert javaFileAssert = JavaFileAssert.assertThat(files.get("TestApi.java"));
         javaFileAssert
@@ -3347,7 +3346,7 @@ public void testXPatternMessage_issue5857() throws IOException {
         generator.setGeneratorPropertyDefault(CodegenConstants.MODELS, "true");
 
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert javaFileAssert = JavaFileAssert.assertThat(files.get("ObjTest.java"));
         javaFileAssert
@@ -3391,7 +3390,7 @@ public void testXPatternMessage_issue18959() throws IOException {
         generator.setGenerateMetadata(false); // skip metadata generation
 
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert javaFileAssert = JavaFileAssert.assertThat(files.get("TestApi.java"));
         javaFileAssert
@@ -3445,7 +3444,7 @@ public void testEnumCaseInsensitive_issue8084() throws IOException {
         generator.setGeneratorPropertyDefault(CodegenConstants.MODELS, "true");
 
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert javaFileAssert = JavaFileAssert.assertThat(files.get("EnumTest.java"));
         javaFileAssert
@@ -3478,7 +3477,7 @@ public void testEnumCaseSensitive_issue8084() throws IOException {
         generator.setGeneratorPropertyDefault(CodegenConstants.MODELS, "true");
 
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert javaFileAssert = JavaFileAssert.assertThat(files.get("EnumTest.java"));
         javaFileAssert
@@ -3512,7 +3511,7 @@ public void testHasOperationParameterExtraAnnotation_issue18224() throws IOExcep
         generator.setGeneratorPropertyDefault(CodegenConstants.APIS, "true");
 
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert javaFileAssert = JavaFileAssert.assertThat(files.get("TestApi.java"));
         javaFileAssert
@@ -3557,7 +3556,7 @@ public void testModelHasParameterExtraAnnotations_issue19953() {
         generator.setGeneratorPropertyDefault(CodegenConstants.MODELS, "true");
 
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert javaFileAssert = JavaFileAssert.assertThat(files.get("ObjTest.java"));
         javaFileAssert.assertProperty("field3")
@@ -3592,7 +3591,7 @@ public void testHasOperationExtraAnnotation_issue15822() throws IOException {
         generator.setGeneratorPropertyDefault(CodegenConstants.APIS, "true");
 
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert javaFileAssert = JavaFileAssert.assertThat(files.get("TestApi.java"));
         javaFileAssert
@@ -3627,7 +3626,7 @@ public void testHasOperationExtraAnnotation_issue12219() throws IOException {
         generator.setGeneratorPropertyDefault(CodegenConstants.APIS, "true");
 
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert javaFileAssert = JavaFileAssert.assertThat(files.get("TestApi.java"));
         javaFileAssert
@@ -3664,7 +3663,7 @@ public void testHasOperationExtraAnnotation_issue12219_array() throws IOExceptio
         generator.setGeneratorPropertyDefault(CodegenConstants.APIS, "true");
 
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert javaFileAssert = JavaFileAssert.assertThat(files.get("TestApi.java"));
         javaFileAssert
@@ -4754,7 +4753,7 @@ public void testSSEOperationSupport() throws Exception {
         generator.setGenerateMetadata(false);
 
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         MapAssert.assertThatMap(files).isNotEmpty();
         File api = files.get("PathApi.java");
@@ -5112,7 +5111,7 @@ public void optionalListShouldBeEmpty() throws IOException {
         generator.setGeneratorPropertyDefault(CodegenConstants.MODELS, "true");
 
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("PetDto.java"))
                 .fileContains("private List<@Valid TagDto> tags = new ArrayList<>();")
@@ -5146,7 +5145,7 @@ public void testCollectionTypesWithDefaults_issue_18102() throws IOException {
         generator.setGeneratorPropertyDefault(CodegenConstants.MODELS, "true");
 
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("PetDto.java"))
                 .fileContains("private @Nullable List<@Valid TagDto> tags")
@@ -5561,7 +5560,7 @@ public void testEnumWithImplements() {
         codegen.setOutputDir(output.toString());
 
         Map<String, File> files = new DefaultGenerator().opts(new ClientOptInput().openAPI(openAPI).config(codegen))
-                .generate().stream().collect(Collectors.toMap(File::getName, Function.identity()));
+                .generate().stream().collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("Type.java")).fileContains("Type implements java.io.Serializable {");
     }
@@ -5706,7 +5705,7 @@ public void testCollectionTypesWithDefaults_issue_collection() throws IOExceptio
 
         DefaultGenerator generator = new DefaultGenerator();
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("PetDto.java"))
                 .fileContains("private @Nullable List<@Valid TagDto> tags;")
@@ -5733,7 +5732,7 @@ public void testDefaultForRequiredNonNullableMap() throws IOException {
 
         DefaultGenerator generator = new DefaultGenerator();
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert.assertThat(files.get("Pet.java"))
                 .fileContains("private Map<String, String> requiredNonNullableMap = new HashMap<>();");
@@ -5802,7 +5801,7 @@ public void testHasRestControllerDoesNotHaveController_issue21156() throws IOExc
         generator.setGeneratorPropertyDefault(CodegenConstants.APIS, "true");
 
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert javaFileAssert = JavaFileAssert.assertThat(files.get("TestApiDelegate.java"));
         javaFileAssert
@@ -6174,7 +6173,7 @@ public void annotationLibraryDoesNotCauseImportConflictsInSpring() throws IOExce
         DefaultGenerator generator = new DefaultGenerator();
 
         Map<String, File> files = generator.opts(input).generate().stream()
-            .collect(Collectors.toMap(File::getName, Function.identity()));
+            .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         File apiFile = files.get("Schema.java");
         assertNotNull(apiFile);
@@ -6208,7 +6207,7 @@ public void annotationLibraryDoesNotCauseImportConflictsInSpringWithAnnotationLi
         DefaultGenerator generator = new DefaultGenerator();
 
         Map<String, File> files = generator.opts(input).generate().stream()
-            .collect(Collectors.toMap(File::getName, Function.identity()));
+            .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         File apiFile = files.get("Schema.java");
         assertNotNull(apiFile);
@@ -6244,7 +6243,7 @@ public void testExtensionsOnSchema_issue9183() throws IOException {
         generator.setGenerateMetadata(false); // skip metadata generation
 
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         JavaFileAssert javaFileAssert = JavaFileAssert.assertThat(files.get("TestApi.java"));
         javaFileAssert
@@ -6289,7 +6288,7 @@ public void shouldAddNullableImportForArrayTypeModels() throws IOException {
         generator.setGeneratorPropertyDefault(CodegenConstants.MODEL_DOCS, "false");
 
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         // AnimalFarm is an array-type model with no properties (issue #22788)
         JavaFileAssert.assertThat(files.get("AnimalFarm.java"))
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/kotlin/spring/KotlinSpringServerCodegenTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/kotlin/spring/KotlinSpringServerCodegenTest.java
index 353c5141c910..654c2b5e29e6 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/kotlin/spring/KotlinSpringServerCodegenTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/kotlin/spring/KotlinSpringServerCodegenTest.java
@@ -35,13 +35,10 @@
 import java.util.List;
 import java.util.Map;
 import java.util.function.Consumer;
-import java.util.function.Function;
-import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
 import static org.assertj.core.api.Assertions.assertThat;
-import static org.openapitools.codegen.TestUtils.assertFileContains;
-import static org.openapitools.codegen.TestUtils.assertFileNotContains;
+import static org.openapitools.codegen.TestUtils.*;
 import static org.openapitools.codegen.languages.KotlinSpringServerCodegen.*;
 import static org.openapitools.codegen.languages.SpringCodegen.REACTIVE;
 import static org.openapitools.codegen.languages.SpringCodegen.SPRING_BOOT;
@@ -803,7 +800,7 @@ public void useBeanValidationGenerateAnnotationsForRequestBody() throws IOExcept
 
         DefaultGenerator generator = new DefaultGenerator();
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         assertFileContains(
                 Paths.get(files.get("AddApi.kt").getAbsolutePath()),
@@ -4153,7 +4150,7 @@ private Map<String, File> generateFromContract(
         generatorPropertyDefaults.forEach(generator::setGeneratorPropertyDefault);
 
         return generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
     }
 
     // ========== AUTO X-SPRING-PAGINATED TESTS ==========
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/php/PhpClientCodegenTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/php/PhpClientCodegenTest.java
index 991dd174515c..386e97cc2702 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/php/PhpClientCodegenTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/php/PhpClientCodegenTest.java
@@ -30,9 +30,10 @@
 import java.nio.file.Files;
 import java.util.List;
 import java.util.Map;
-import java.util.function.Function;
 import java.util.stream.Collectors;
 
+import static org.openapitools.codegen.TestUtils.collectToCaseInsensitiveOrderedCaseSensitiveKeyMap;
+
 public class PhpClientCodegenTest {
 
     protected PhpClientCodegen codegen;
@@ -123,7 +124,7 @@ public void testEnumUnknownDefaultCaseDeserializationEnabled() throws Exception
 
         DefaultGenerator generator = new DefaultGenerator();
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         List<String> modelContent = Files
                 .readAllLines(files.get("Pet.php").toPath())
@@ -151,7 +152,7 @@ public void testEnumUnknownDefaultCaseDeserializationDisabled() throws Exception
 
         DefaultGenerator generator = new DefaultGenerator();
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         List<String> modelContent = Files
                 .readAllLines(files.get("Pet.php").toPath())
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/php/PhpNextgenClientCodegenTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/php/PhpNextgenClientCodegenTest.java
index 02f58f48f64e..3ee449890664 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/php/PhpNextgenClientCodegenTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/php/PhpNextgenClientCodegenTest.java
@@ -33,9 +33,10 @@
 import java.nio.file.Files;
 import java.util.List;
 import java.util.Map;
-import java.util.function.Function;
 import java.util.stream.Collectors;
 
+import static org.openapitools.codegen.TestUtils.collectToCaseInsensitiveOrderedCaseSensitiveKeyMap;
+
 public class PhpNextgenClientCodegenTest {
 
     protected PhpNextgenClientCodegen codegen;
@@ -108,7 +109,7 @@ public void testEnumUnknownDefaultCaseDeserializationEnabled() throws Exception
 
         DefaultGenerator generator = new DefaultGenerator();
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         List<String> modelContent = Files
                 .readAllLines(files.get("Pet.php").toPath())
@@ -136,7 +137,7 @@ public void testEnumUnknownDefaultCaseDeserializationDisabled() throws Exception
 
         DefaultGenerator generator = new DefaultGenerator();
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         List<String> modelContent = Files
                 .readAllLines(files.get("Pet.php").toPath())
@@ -165,7 +166,7 @@ public void testDifferentResponseSchemasWithEmpty() throws IOException {
 
         DefaultGenerator generator = new DefaultGenerator();
         Map<String, File> files = generator.opts(input).generate().stream()
-                .collect(Collectors.toMap(File::getName, Function.identity()));
+                .collect(collectToCaseInsensitiveOrderedCaseSensitiveKeyMap());
 
         List<String> modelContent = Files
                 .readAllLines(files.get("DefaultApi.php").toPath())