Lab 6.07: CI with GitHub Actions

Duration: 2h | Type: Lab

Lab Overview

In this lab you will create a Continuous Integration pipeline for the actions project — a Spring Boot REST API backed by an H2 in-memory database using GitHub Actions. You will write a workflow file that automatically builds and tests the application every time code is pushed to main or a pull request is opened. You will watch the pipeline succeed, intentionally break it, fix it, and add a manual trigger. By the end, your repository will have a working CI pipeline that catches broken code before it reaches the main branch.

Learning Objectives

• Create the .github/workflows/ directory structure in a project
• Write a GitHub Actions workflow file with proper YAML syntax
• Configure triggers for push events, pull requests, and manual dispatch
• Set up JDK 17 and Maven dependency caching in a pipeline
• Use an H2 in-memory database in CI without any external services
• Read pipeline logs to diagnose build failures
• Add a workflow status badge to a .md file

Prerequisites

• This project pushed to a GitHub repository
• Tests passing locally (mvnw test or running them on IntelliJ)
• A GitHub account with access to the Actions tab

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Project Structure

actions/
├── .github/
│   └── workflows/           <-- workflow files go here
├── src/
│   ├── main/
│   │   ├── java/com/example/actions/
│   │   │   ├── controller/TvShowController.java
│   │   │   ├── model/TvShow.java
│   │   │   ├── repository/TvShowRepository.java
│   │   │   └── service/TvShowService.java
│   │   └── resources/
│   │       ├── application.properties   (H2 config + seed toggle)
│   │       └── data.sql                 (15 seeded TV shows)
│   └── test/
│       └── java/com/example/actions/
│           ├── controller/TvShowControllerTest.java
│           └── service/TvShowServiceTest.java
└── pom.xml

The app exposes a single endpoint:

Method	Path	Description
GET	/tvshows	Returns all TV shows

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Instructions

Task 1: Create the Workflow Directory

GitHub Actions only looks for workflow files in one specific location.

1. Create Directory Structure

   In your project root, create the .github/workflows/ directory.

   Hint: The -p flag creates parent directories as needed (macOS/Linux). On Windows use mkdir .github\workflows.

2. Verify Structure

   actions/
   ├── .github/
   │   └── workflows/       <-- workflow files go here
   ├── src/
   └── pom.xml
   

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Task 2: Write the CI Workflow

Create a file at .github/workflows/ci.yml.

Required File Structure:

name: [Your workflow name]

on:
  # Triggers here

jobs:
  build-and-test:
    runs-on: ubuntu-latest

    steps:
      # Steps here

Workflow Requirements:

Metadata:

• Name: Give your workflow a descriptive name (e.g., "Actions App CI")

Triggers (under on:):

• Run on pushes to the main branch
• Run on pull requests targeting the main branch

Job Configuration:

• Single job named build-and-test
• Runs on ubuntu-latest

Steps (in this exact order):

1. Checkout the code

   • Use: actions/checkout@v4

2. Set up JDK 17

   • Use: actions/setup-java@v4
   • Required parameters:
     • distribution: 'temurin'
     • java-version: '17'

3. Cache Maven dependencies

   • Use: actions/cache@v4
   • Required parameters:
     • path: ~/.m2/repository
     • key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}
     • restore-keys: ${{ runner.os }}-maven-

4. Build and test

   • Run: mvn clean verify
   • No database service container is needed. The app uses H2 in-memory, which is on the classpath

Important Considerations:

• YAML is whitespace-sensitive; use exactly 2 spaces for indentation
• Each step must have a name and either uses or run
• Because the project uses H2 (not MySQL), CI requires zero external services

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Task 3: Push and Watch

1. Stage, commit, and push your workflow file to main
2. Go to the Actions tab on GitHub
3. Click into the run → click the build-and-test job → expand each step

What to look for:

• Cache Maven dependencies: says "Cache not found" on first run (expected)
• Build and test: all tests green, BUILD SUCCESS

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Task 4: Break It on Purpose

Proving that CI catches failures is as important as seeing it pass.

1. Introduce a Test Failure

   Open TvShowControllerTest.java and change an assertion to use a wrong value:

   .andExpect(jsonPath("$[0].title").value("Wrong Title"))

2. Commit and push: watch the Actions tab show a red ✗

3. Inspect the Failure: expand the Build and test step and read the assertion mismatch in the Maven output

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Task 5: Fix It

1. Revert the broken assertion
2. Commit and push the fix
3. Watch the pipeline go green again
4. Take a screenshot of the Actions tab showing at least one red ✗ and one green ✓ run

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Task 6: Add Manual Trigger

Add workflow_dispatch to the on: section so the pipeline can be triggered from the GitHub UI without a push:

on:
  push:
    branches: [main]
  pull_request:
    branches: [main]
  workflow_dispatch:

After pushing, go to Actions → your workflow → Run workflow.

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Task 7: Verify Caching

On any run after the first:

• Expand the Cache Maven dependencies step
• Confirm it says "Cache restored from key: ..." rather than "Cache not found"
• Compare build durations: first run (~60–90 s) vs. cached runs (~30–45 s)

Cache invalidates automatically when pom.xml changes (the key includes hashFiles('**/pom.xml')).

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Task 8: Review Your Workflow

Checklist:

• File exists at .github/workflows/ci.yml
• Workflow has a descriptive name
• Checkout uses actions/checkout@v4
• JDK setup uses actions/setup-java@v4 with distribution: 'temurin' and java-version: '17'
• Cache step uses actions/cache@v4 with correct path, key, and restore-keys
• Build step runs mvn clean verify
• All three triggers present: push, pull_request, workflow_dispatch
• YAML indentation is consistent (2 spaces per level)
• Pipeline runs successfully end-to-end

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Deliverable

Push the following to your GitHub repository:

• .github/workflows/ci.yml
• Screenshots from the GitHub Actions tab showing a passing build (green ✓) and a failing build (red ✗) at the end of this readme file.

Submit the repository URL.

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Bonus (Optional)

Add a build status badge to the top of this README.

1. Go to Actions → select your workflow → click "..." → "Create status badge"
2. Copy the Markdown snippet and paste it at the top of README.md
3. Commit and push

Example:

![CI](https://github.com/username/actions/workflows/Actions%20App%20CI/badge.svg)

The badge updates in real-time with each pipeline run.

Super extra bonus (if you get bored 😅)

Check the README-BONUS.md and complete as many exercises as you can.