Jenkinsfile per branch - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Output of Jenkinsfile branch condition

Given this Jenkinsfile snippet, what will be the output when the branch is 'feature-xyz'?

Jenkins

pipeline {
  agent any
  stages {
    stage('Build') {
      when {
        branch 'main'
      }
      steps {
        echo 'Building main branch'
      }
    }
    stage('Feature Build') {
      when {
        branch pattern: 'feature-.*', comparator: 'regex'
      }
      steps {
        echo 'Building feature branch'
      }
    }
  }
}

A No output

B Building main branch

C Building feature branch

D Build failed with error

💡 Hint

Check the branch conditions in the 'when' blocks.

The 'when' condition for the 'Feature Build' stage uses a regex pattern matching branches starting with 'feature-'. Since the branch is 'feature-xyz', this stage runs and outputs 'Building feature branch'. The 'Build' stage only runs on 'main' branch.

❓ Configuration

intermediate

Correct Jenkinsfile syntax for per-branch pipeline

Which Jenkinsfile snippet correctly runs different stages for 'main' and 'develop' branches?

A

pipeline {
  agent any
  stages {
    stage('Main Build') {
      when { branch 'main' }
      steps { echo 'Build main' }
    }
    stage('Develop Build') {
      when { branch 'develop' }
      steps { echo 'Build develop' }
    }
  }
}

B

pipeline {
  agent any
  stages {
    stage('Build') {
      when { branch 'main' || branch 'develop' }
      steps { echo 'Build main or develop' }
    }
  }
}

C

pipeline {
  agent any
  stages {
    stage('Main Build') {
      when { branch == 'main' }
      steps { echo 'Build main' }
    }
    stage('Develop Build') {
      when { branch == 'develop' }
      steps { echo 'Build develop' }
    }
  }
}

D

pipeline {
  agent any
  stages {
    stage('Build') {
      when { branch 'main' && branch 'develop' }
      steps { echo 'Build both' }
    }
  }
}

💡 Hint

Check the syntax of the 'when' condition for branch matching.

Option A uses the correct 'when { branch 'branchName' }' syntax for each stage. Option A tries to combine branches with '||' which is invalid syntax. Option A uses 'branch == 'main'' which is not valid in declarative pipeline. Option A uses '&&' which is invalid for branch condition.

❓ Troubleshoot

advanced

Why does the Jenkinsfile fail on branch detection?

This Jenkinsfile snippet fails with a syntax error. What is the cause?

Jenkins

pipeline {
  agent any
  stages {
    stage('Build') {
      when {
        branch == 'main'
      }
      steps {
        echo 'Building main'
      }
    }
  }
}

A Agent declaration is incorrect

B Using 'branch == 'main'' is invalid syntax in 'when' condition

C Missing 'steps' block inside 'stage'

D Pipeline block is missing 'environment' section

💡 Hint

Check the syntax rules for 'when' branch condition in declarative pipeline.

The 'when' condition for branch must use 'branch 'branchName'' syntax, not an equality check like 'branch == 'main''. This causes a syntax error.

🔀 Workflow

advanced

Jenkinsfile multi-branch pipeline behavior

In a multi-branch pipeline, what happens if a Jenkinsfile contains a 'when' condition that excludes the current branch?

A The stage is skipped and pipeline continues with other stages

B Jenkins retries the pipeline on a different branch automatically

C The entire pipeline is skipped and marked as success

D The pipeline fails immediately with an error

💡 Hint

Think about how 'when' conditions control stage execution.

Stages with 'when' conditions that do not match the current branch are simply skipped. The pipeline continues running other stages that match or have no conditions.

✅ Best Practice

expert

Best practice for managing Jenkinsfiles per branch

What is the recommended approach to maintain different Jenkinsfiles for multiple branches in a Git repository?

A Duplicate the entire repository per branch with its own Jenkinsfile

B Create separate Jenkinsfiles named Jenkinsfile-main, Jenkinsfile-develop, and switch Jenkinsfile path in Jenkins config per branch

C Store Jenkinsfiles in separate folders per branch and configure Jenkins to load from those folders

D Use a single Jenkinsfile with 'when' conditions to handle branch-specific logic

💡 Hint

Consider maintainability and Jenkins multi-branch pipeline features.

Using a single Jenkinsfile with 'when' conditions is the best practice. It keeps configuration centralized and leverages Jenkins multi-branch pipeline features. Other options increase complexity and maintenance overhead.