Great! Let’s go through a basic example of GitLab CI/CD pipeline YAML that demonstrates how the stages keyword is used.

🔧 What is stages in GitLab CI/CD?

The stages keyword defines the sequence of execution in your pipeline. Jobs are grouped under these stages, and GitLab runs the stages in order: one must complete successfully before the next begins.

✅ Basic GitLab CI YAML Example

stages:
  - build
  - test
  - deploy

# Job in "build" stage
build-job:
  stage: build
  script:
    - echo "Compiling the app..."
    - echo "Build complete!"

# Job in "test" stage
test-job:
  stage: test
  script:
    - echo "Running unit tests..."
    - echo "All tests passed!"

# Job in "deploy" stage
deploy-job:
  stage: deploy
  script:
    - echo "Deploying the app..."
    - echo "Deployment successful!"
Code language: PHP (php)

📘 Explanation

🔹 stages Section

stages:
  - build
  - test
  - deploy

• This declares three sequential stages: build, test, and deploy.
• GitLab will execute jobs in this order, waiting for all jobs in one stage to pass before moving to the next.

🔹 Jobs and Their Assigned Stages

build-job:

build-job:
  stage: build
  script:
    - echo "Compiling the app..."
Code language: PHP (php)

• This job is part of the build stage and will run first.

test-job:

test-job:
  stage: test
  script:
    - echo "Running unit tests..."
Code language: PHP (php)

• This runs only after all build jobs succeed.

deploy-job:

deploy-job:
  stage: deploy
  script:
    - echo "Deploying the app..."
Code language: PHP (php)

• This runs last, only if all test jobs succeed.

🧠 Key Notes

• If a stage has multiple jobs, GitLab runs them in parallel (if runners are available).
• If any job in a stage fails, subsequent stages are skipped.
• You must explicitly assign stage: to every job (or it defaults to test if not defined).