pre-push hook in Git - Mini Project: Build & Apply

Create a Git Pre-Push Hook to Run Tests

📖 Scenario: You are working on a team project using Git. To keep the code quality high, you want to run tests automatically before pushing any changes to the remote repository.This will help catch errors early and avoid broken code being shared.

🎯 Goal: Build a Git pre-push hook script that runs a test command before allowing a push.If the tests fail, the push should be stopped.

📋 What You'll Learn

Create a pre-push hook file in the .git/hooks directory

Make the hook file executable

Add a test command inside the hook script

Ensure the push is blocked if tests fail

💡 Why This Matters

🌍 Real World

Pre-push hooks help teams catch errors early by running tests automatically before code is shared.

💼 Career

Knowing how to write Git hooks is useful for DevOps roles and software developers to enforce quality checks.

1

Create the pre-push hook file

Create a file named pre-push inside the .git/hooks directory with the first line #!/bin/sh to specify the shell interpreter.

Git

# Create the pre-push hook file with the shebang line
# Your code here

Hint

The first line of a shell script should be #!/bin/sh to tell Git which shell to use.

2

Add a test command variable

Inside the pre-push file, add a variable named TEST_COMMAND and set it to npm test.

Git

#!/bin/sh
# Add the TEST_COMMAND variable
# Your code here

Hint

Use TEST_COMMAND="npm test" to store the test command in a variable.

3

Run the test command and check result

Add code to run the $TEST_COMMAND and check if it succeeds. If it fails, print Tests failed, push aborted. and exit with status 1.

Git

#!/bin/sh
TEST_COMMAND="npm test"
# Run tests and abort push if tests fail
# Your code here

Hint

Use if ! $TEST_COMMAND; then ... fi to run the tests and handle failure.

4

Print success message after tests pass

Add a line to print Tests passed, pushing changes... after the tests succeed.

Git

#!/bin/sh
TEST_COMMAND="npm test"

if ! $TEST_COMMAND; then
  echo "Tests failed, push aborted."
  exit 1
fi
# Print success message
# Your code here

Hint

Use echo "Tests passed, pushing changes..." to show the success message.

Practice

1. What is the main purpose of a pre-push hook in Git?

easy

A. To delete local branches after pushing

B. To merge branches automatically before pushing

C. To run checks or tests before code is pushed to a remote repository

D. To create a backup of the repository before pushing

Solution

1. Step 1: Understand the role of pre-push hooks

   Pre-push hooks run scripts before pushing code to a remote repository to catch errors early.

2. Step 2: Identify the correct purpose

   They help ensure code quality by running tests or checks before the push happens.

3. Final Answer:

   To run checks or tests before code is pushed to a remote repository -> Option C

4. Quick Check:

   Pre-push hook = run checks before push [OK]

Hint: Pre-push hooks run before push to catch problems early [OK]

Common Mistakes:

• Confusing pre-push with post-push hooks
• Thinking it merges branches automatically
• Assuming it deletes branches

2. Which of the following is the correct way to make a pre-push hook script executable on Linux or macOS?

easy

A. chmod +x .git/hooks/pre-push

B. git enable pre-push

C. chmod 777 .git/hooks/pre-push

D. git hook activate pre-push

Solution

1. Step 1: Identify how to make scripts executable

   On Linux/macOS, chmod +x sets execute permission on a file.

2. Step 2: Apply to pre-push hook

   Running chmod +x .git/hooks/pre-push makes the hook script runnable by Git.

3. Final Answer:

   chmod +x .git/hooks/pre-push -> Option A

4. Quick Check:

   Make hook executable = chmod +x [OK]

Hint: Use chmod +x to make hook scripts executable [OK]

Common Mistakes:

• Using git commands that don't exist for hooks
• Setting overly permissive permissions like 777
• Forgetting to make the script executable

3. Given this pre-push hook script snippet, what will happen if the tests fail?

#!/bin/sh
npm test || exit 1

medium

A. The push will continue regardless of test results

B. The script will delete the remote branch

C. The tests will be skipped

D. The push will be blocked and stopped

Solution

1. Step 1: Understand the script logic

   The script runs npm test. If tests fail, npm test returns non-zero, triggering exit 1.

2. Step 2: Effect of exit 1 in pre-push hook

   Exiting with a non-zero code stops the push process, blocking the push.

3. Final Answer:

   The push will be blocked and stopped -> Option D

4. Quick Check:

   Exit 1 in pre-push = block push [OK]

Hint: Exit non-zero in pre-push stops the push [OK]

Common Mistakes:

• Assuming push continues even if tests fail
• Thinking tests are skipped automatically
• Confusing exit codes with success

4. You wrote a pre-push hook script but it does not run when you push. What is the most likely cause?

medium

A. The remote repository is down

B. The script is missing execute permissions

C. You forgot to commit your changes

D. The branch name is incorrect

Solution

1. Step 1: Check script execution requirements

   Git requires hook scripts to have execute permission to run them.

2. Step 2: Identify common cause of hook not running

   If the script lacks execute permission, Git silently skips running it.

3. Final Answer:

   The script is missing execute permissions -> Option B

4. Quick Check:

   Missing execute permission = hook won't run [OK]

Hint: Check execute permission if hook doesn't run [OK]

Common Mistakes:

• Blaming remote repository for local hook issues
• Thinking commit status affects hook execution
• Assuming branch name affects hook running

5. You want your pre-push hook to run tests only on files changed in the last commit before pushing. Which approach is best?

hard

A. Use git diff --name-only HEAD~1 HEAD inside the hook to get changed files and run tests accordingly

B. Run tests on all files every time without checking changes

C. Manually list files in the hook script each time

D. Push first, then run tests on the remote repository

Solution

1. Step 1: Identify how to detect changed files

   The command git diff --name-only HEAD~1 HEAD lists files changed in the last commit.

2. Step 2: Use this command in pre-push hook

   Using this inside the hook lets you run tests only on changed files, saving time and resources.

3. Final Answer:

   Use git diff --name-only HEAD~1 HEAD inside the hook to get changed files and run tests accordingly -> Option A

4. Quick Check:

   Detect changed files with git diff for selective tests [OK]

Hint: Use git diff to find changed files for selective tests [OK]

Common Mistakes:

• Running tests on all files unnecessarily
• Manually updating file lists each time
• Running tests after push instead of before