GitHub Actions: Testing a Dockerfile

Goal

The goal of this exercise is to create a GitHub Action that tests a Dockerfile for a Spring Boot application.

Step 1: Create a new workflow file

Inside the .github/workflows directory, create a new file named docker-ci.yml.

Open the docker-ci.yml file and add the following content:

name: Docker CI
on:
  push:
    branches:
      - main
  pull_request:
    branches:
      - main

jobs:
  build:
    runs-on: ubuntu-latest
    permissions:
      contents: read
    steps:
      - name: Checkout code
        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2

      - name: Build Docker image
        run: docker build -t app:test .

      - name: Run Docker container
        run: |
          # Run the container in detached mode
          docker compose up -d
          
          # Wait for a few seconds to ensure the container is up and running
          sleep 20

          # Test the application endpoint
          curl -f http://localhost:8090/actuator/health || exit 1

          # Stop and remove the container
          docker compose down

The pipe (|) in the run step allows you to write multi-line shell commands.

Step 2: Commit and Push

For the action to take effect, you need to commit and push the changes to your repository. You can do this using the following commands:

git add .
git commit -m "Add Docker CI GitHub Action"
git push

Step 3: Verify the Action

1. Go to your GitHub repository in your web browser.
2. Click on the "Actions" tab.
3. You should see a new workflow run for the "Docker CI" action. Click on it to see the details.
4. Click on the job to see the logs. You should see the steps for checking out the code, building the Docker image, running the container, and testing the application endpoint.