Branch-specific pipeline behavior in Jenkins - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to specify the branch name in the Jenkins pipeline.

Jenkins

pipeline {
    agent any
    stages {
        stage('Build') {
            when {
                branch [1]
            }
            steps {
                echo 'Building branch'
            }
        }
    }
}

Drag options to blanks, or click blank then click option'

A'feature'

B'develop'

C'main'

D'release'

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to use quotes around the branch name

Using the wrong branch name

The branch condition expects the branch name as a string. Here, 'main' is the correct branch to trigger the build.

2fill in blank

medium

Complete the code to run the stage only on the 'develop' branch.

Jenkins

stage('Test') {
    when {
        branch [1]
    }
    steps {
        echo 'Running tests on develop branch'
    }
}

Drag options to blanks, or click blank then click option'

A'develop'

B'main'

C'feature'

D'hotfix'

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong branch name

Omitting quotes around the branch name

The when condition with branch 'develop' ensures this stage runs only on the develop branch.

3fill in blank

hard

Fix the error in the branch condition to correctly check for the 'feature' branch.

Jenkins

when {
    branch [1]
}

Drag options to blanks, or click blank then click option'

A'feature'

Bfeature

C"feature"

Dbranch == 'feature'

Attempts:

3 left

💡 Hint

Common Mistakes

Not using quotes around the branch name

Using an expression instead of a string

The branch name must be a string literal in quotes. Using 'feature' is correct syntax.

4fill in blank

hard

Fill both blanks to run the stage only on branches starting with 'release' and skip others.

Jenkins

stage('Deploy') {
    when {
        expression {
            return env.BRANCH_NAME.[1]('release') [2] true
        }
    }
    steps {
        echo 'Deploying release branch'
    }
}

Drag options to blanks, or click blank then click option'

AstartsWith

B==

C!=

Dcontains

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'contains' instead of 'startsWith'

Not comparing the result to true

The startsWith method checks if the branch name begins with 'release'. The == true ensures the expression returns a boolean.

5fill in blank

hard

Fill all three blanks to create a pipeline that runs different stages for 'main', 'develop', and other branches.

Jenkins

pipeline {
    agent any
    stages {
        stage('Build') {
            when {
                branch [1]
            }
            steps {
                echo 'Building main branch'
            }
        }
        stage('Test') {
            when {
                branch [2]
            }
            steps {
                echo 'Testing develop branch'
            }
        }
        stage('Deploy') {
            when {
                not {
                    branch [3]
                }
            }
            steps {
                echo 'Deploying other branches'
            }
        }
    }
}

Drag options to blanks, or click blank then click option'

A'main'

B'develop'

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up branch names in stages

Not using quotes around branch names

The first stage runs on 'main', the second on 'develop', and the deploy stage runs on branches that are not 'develop'.

Practice

1.

Which Jenkins pipeline syntax runs a stage only on the main branch?

easy

A. branch == 'main' { runStage() }

B. if (branch == 'main')

C. onlyIf branch == 'main'

D. when { branch 'main' }

Solution

1. Step 1: Understand Jenkins branch condition syntax

   Jenkins uses when { branch 'branchName' } to run stages on specific branches.

2. Step 2: Match syntax to run on main branch

   The correct syntax is when { branch 'main' } to target the main branch.

3. Final Answer:

   when { branch 'main' } -> Option D

4. Quick Check:

   Branch condition = when { branch 'main' } [OK]

Hint: Use 'when { branch "branchName" }' for branch-specific stages [OK]

Common Mistakes:

• Using if statements instead of 'when' block
• Incorrect syntax like 'onlyIf' or inline conditions
• Confusing branch name quotes or missing quotes

2.

Which snippet correctly uses Jenkins declarative pipeline syntax to run a stage only on branches dev or feature/*?

stage('Test') {
  when {
    ???
  }
  steps {
    echo 'Running tests'
  }
}

easy

A. anyOf { branch 'dev'; branch 'feature/*' }

B. branch 'dev' && branch 'feature/*'

C. allOf { branch 'dev'; branch 'feature/*' }

D. branch 'dev' || branch 'feature/*'

Solution

1. Step 1: Identify correct syntax for multiple branch conditions

   Jenkins uses anyOf { branch 'name'; branch 'pattern' } to run if any branch matches.

2. Step 2: Choose syntax matching either 'dev' or 'feature/*'

   Using anyOf { branch 'dev'; branch 'feature/*' } runs the stage on either branch.

3. Final Answer:

   anyOf { branch 'dev'; branch 'feature/*' } -> Option A

4. Quick Check:

   Multiple branches = anyOf with branch conditions [OK]

Hint: Use anyOf { branch 'x'; branch 'y' } for multiple branches [OK]

Common Mistakes:

• Using logical operators like || or && directly inside when
• Using allOf which requires all conditions true
• Incorrect syntax without braces or semicolons

3.

Given this Jenkins pipeline snippet, what will be the output if the branch is feature/login?

pipeline {
  agent any
  stages {
    stage('Build') {
      when { branch 'main' }
      steps { echo 'Building main branch' }
    }
    stage('Test') {
      when { branch 'feature/*' }
      steps { echo 'Testing feature branch' }
    }
  }
}

medium

A. Testing feature branch

B. Building main branch

C. Building main branch\nTesting feature branch

D. No output

Solution

1. Step 1: Check branch conditions for each stage

   'Build' runs only on 'main' branch; 'Test' runs on branches matching 'feature/*'.

2. Step 2: Match current branch 'feature/login'

   'feature/login' matches 'feature/*', so only 'Test' stage runs and prints 'Testing feature branch'.

3. Final Answer:

   Testing feature branch -> Option A

4. Quick Check:

   Branch 'feature/login' matches 'feature/*' only [OK]

Hint: Match branch patterns carefully to predict stage execution [OK]

Common Mistakes:

• Assuming 'main' stage runs on all branches
• Ignoring wildcard pattern matching
• Expecting both stages to run always

4.

Identify the error in this Jenkins pipeline snippet that tries to run a stage only on the release branch:

stage('Deploy') {
  when {
    branch release
  }
  steps {
    echo 'Deploying release branch'
  }
}

medium

A. Steps block should be outside the stage

B. Incorrect stage name 'Deploy'

C. Missing quotes around branch name in when condition

D. Branch condition should be inside steps

Solution

1. Step 1: Review syntax for branch condition in when block

   The branch name must be a string inside quotes: branch 'release'.

2. Step 2: Identify missing quotes causing syntax error

   Here, branch release lacks quotes, causing a syntax error.

3. Final Answer:

   Missing quotes around branch name in when condition -> Option C

4. Quick Check:

   Branch names need quotes in when { branch 'name' } [OK]

Hint: Always quote branch names in when { branch 'name' } [OK]

Common Mistakes:

• Omitting quotes around branch names
• Placing steps outside stage block
• Misplacing branch condition inside steps

5.

You want a Jenkins pipeline stage to run on all branches except main and develop. Which when condition correctly implements this?

hard

A. allOf { not branch 'main'; not branch 'develop' }

B. not { anyOf { branch 'main'; branch 'develop' } }

C. anyOf { not branch 'main'; not branch 'develop' }

D. branch != 'main' && branch != 'develop'

Solution

1. Step 1: Understand negation of multiple branches

   To exclude branches, wrap the branches in anyOf and negate with not.

2. Step 2: Apply correct syntax for excluding 'main' and 'develop'

   not { anyOf { branch 'main'; branch 'develop' } } runs on all branches except these two.

3. Final Answer:

   not { anyOf { branch 'main'; branch 'develop' } } -> Option B

4. Quick Check:

   Exclude branches = not { anyOf { ... } } [OK]

Hint: Use not { anyOf { branch 'x'; branch 'y' } } to exclude branches [OK]

Common Mistakes:

• Using allOf with negations incorrectly
• Using logical operators like && directly
• Misplacing not inside anyOf instead of outside