GitLab CI basics - Mini Project: Build & Apply

GitLab CI basics

📖 Scenario: You are working on a small project and want to automate testing using GitLab CI. You will create a simple GitLab CI configuration file to run a test job automatically when you push code.

🎯 Goal: Build a basic .gitlab-ci.yml file that defines a job named test which runs a simple shell command echo "Running tests...".

📋 What You'll Learn

Create a .gitlab-ci.yml file with a job named test

The test job must run the command echo "Running tests..."

Use the script keyword to define the command

Ensure the job runs in the test stage

💡 Why This Matters

🌍 Real World

GitLab CI is used to automate testing and deployment in software projects, saving time and reducing errors.

💼 Career

Understanding GitLab CI basics is essential for DevOps roles and developers working with continuous integration pipelines.

1

Create the basic GitLab CI file

Create a file named .gitlab-ci.yml and add the line stages: with a list containing test to define the stages.

Git

# Your code here

Hint

Use YAML syntax to define stages: followed by a list with - test.

2

Add the test job

Add a job named test that runs in the test stage. Use the stage keyword with value test.

Git

stages:
  - test

# Your code here

Hint

Define a job by writing its name followed by stage: test.

3

Add the script to run

Inside the test job, add a script section that runs the command echo "Running tests...".

Git

stages:
  - test

test:
  stage: test
  # Your code here

Hint

Use script: followed by a list with the echo command.

4

Check the job output

Run the GitLab CI pipeline and verify that the output contains the text Running tests.... Write a command to simulate this by printing Running tests....

Git

stages:
  - test

test:
  stage: test
  script:
    - echo "Running tests..."

# Your code here

Hint

Use echo "Running tests..." to show the output.

Practice

1. What is the main purpose of the .gitlab-ci.yml file in GitLab CI?

easy

A. To create branches automatically

B. To store the source code of the project

C. To configure user permissions in GitLab

D. To define the stages and jobs for automated tasks like build and test

Solution

1. Step 1: Understand the role of .gitlab-ci.yml

   This file is used to tell GitLab CI what tasks to run automatically, such as building or testing code.

2. Step 2: Identify what the file does not do

   It does not store code, manage permissions, or create branches; those are handled elsewhere.

3. Final Answer:

   To define the stages and jobs for automated tasks like build and test -> Option D

4. Quick Check:

   .gitlab-ci.yml defines jobs and stages [OK]

Hint: Remember: .gitlab-ci.yml controls automation steps [OK]

Common Mistakes:

• Confusing .gitlab-ci.yml with source code files
• Thinking it manages user permissions
• Assuming it creates branches automatically

2. Which of the following is the correct way to define a job named test in .gitlab-ci.yml?

easy

A. job test {
run: echo "Running tests"
}

B. test:
script:
- echo "Running tests"

C. job:
name: test
command: echo "Running tests"

D. task test:
commands:
- echo "Running tests"

Solution

1. Step 1: Recall GitLab CI job syntax

   A job is defined by its name followed by a script section listing commands to run.

2. Step 2: Compare options to correct YAML format

   test: script: - echo "Running tests" uses correct YAML with job name and script list. Others use incorrect keywords or syntax.

3. Final Answer:

   test: script: - echo "Running tests" -> Option B

4. Quick Check:

   Job name + script list = correct job definition [OK]

Hint: Job name + script list is the YAML way to define jobs [OK]

Common Mistakes:

• Using curly braces or incorrect keywords like 'job' or 'task'
• Not using a list for script commands
• Incorrect indentation or missing colons

3. Given this .gitlab-ci.yml snippet:

stages:
  - build
  - test

build_job:
  stage: build
  script:
    - echo "Building"
test_job:
  stage: test
  script:
    - echo "Testing"

What will be the order of job execution?

medium

A. Both jobs run at the same time

B. test_job runs first, then build_job

C. build_job runs first, then test_job

D. Only build_job runs

Solution

1. Step 1: Understand stages order

   Stages run in the order listed: first 'build', then 'test'.

2. Step 2: Match jobs to stages

   'build_job' is in 'build' stage, so it runs before 'test_job' in 'test' stage.

3. Final Answer:

   build_job runs first, then test_job -> Option C

4. Quick Check:

   Stages run in order listed [OK]

Hint: Jobs run by stage order top to bottom [OK]

Common Mistakes:

• Assuming jobs run in alphabetical order
• Thinking jobs run in parallel by default
• Ignoring the stages list order

4. You wrote this job in .gitlab-ci.yml but it never runs:

deploy_job:
  script:
    - echo "Deploying"
  only:
    - main

What is the likely reason?

medium

A. The job is missing a stage definition

B. The branch name is incorrect; it should be 'master' instead of 'main'

C. The 'only' keyword is deprecated; use 'rules' instead

D. The script command is invalid

Solution

1. Step 1: Check the stage assignment

   The job does not specify a 'stage' key, so it defaults to the 'test' stage.

2. Step 2: Impact of missing stage in global stages

   If the root-level 'stages' does not include 'test', GitLab fails the job because the stage is undefined in the global stages list.

3. Final Answer:

   The job is missing a stage definition -> Option A

4. Quick Check:

   Default stage 'test' must be in 'stages' list [OK]

Hint: Default stage is 'test'; must be defined in 'stages' if used [OK]

Common Mistakes:

• Assuming branch name is wrong without checking
• Forgetting to define a stage (defaults to 'test' if missing)
• Thinking script command syntax is wrong

5. You want a job to run only on the develop branch and after the build stage completes successfully. Which .gitlab-ci.yml snippet correctly achieves this?

hard

A. deploy_job:
stage: deploy
script:
- echo "Deploying"
rules:
- if: '$CI_COMMIT_BRANCH == "develop"'
when: on_success
needs:
- build_job

B. deploy_job:
stage: deploy
script:
- echo "Deploying"
only:
- develop
after_script:
- build_job

C. deploy_job:
stage: deploy
script:
- echo "Deploying"
rules:
- branch: develop
when: always
dependencies:
- build_job

D. deploy_job:
stage: deploy
script:
- echo "Deploying"
except:
- main
needs:
- build

Solution

1. Step 1: Use 'rules' to run job only on 'develop' branch

   The 'rules' keyword with condition '$CI_COMMIT_BRANCH == "develop"' ensures the job runs only on that branch.

2. Step 2: Use 'needs' to wait for 'build_job'

   The 'needs' keyword makes this job wait for 'build_job' to finish successfully before running.

3. Final Answer:

   deploy_job: stage: deploy script: - echo "Deploying" rules: - if: '$CI_COMMIT_BRANCH == "develop"' when: on_success needs: - build_job -> Option A

4. Quick Check:

   'rules' + 'needs' control branch and stage order [OK]

Hint: Use 'rules' for branch and 'needs' for stage dependency [OK]

Common Mistakes:

• Using deprecated 'only' or 'except' keywords
• Confusing 'after_script' with job dependencies
• Incorrect 'needs' or 'dependencies' usage