Stage conditions with when directive in Jenkins - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

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

Jenkins

stage('Build') {
  when {
    branch [1]
  }
  steps {
    echo 'Building...'
  }
}

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

A'main'

B'develop'

C'feature'

D'release'

Attempts:

3 left

💡 Hint

Common Mistakes

Using a branch name other than 'main'.

Omitting quotes around the branch name.

The when directive with branch 'main' ensures the stage runs only on the main branch.

2fill in blank

medium

Complete the code to run the stage only when the environment variable 'DEPLOY' is set to 'true'.

Jenkins

stage('Deploy') {
  when {
    environment name: 'DEPLOY', value: [1]
  }
  steps {
    echo 'Deploying...'
  }
}

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

A'no'

B'false'

C'yes'

D'true'

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'false' or other values instead of 'true'.

Not quoting the value string.

The when directive checks if the environment variable DEPLOY equals 'true' to run the stage.

3fill in blank

hard

Fix the error in the when condition to run the stage only if the branch is 'feature'.

Jenkins

stage('Test') {
  when {
    branch [1]
  }
  steps {
    echo 'Testing...'
  }
}

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

Afeature'

B'feature'

C"feature"

Dfeature

Attempts:

3 left

💡 Hint

Common Mistakes

Not quoting the branch name.

Using mismatched or incomplete quotes.

The branch name must be a quoted string like 'feature' in the when directive to avoid syntax errors.

4fill in blank

hard

Fill both blanks to run the stage only when the branch is 'release' and the environment variable 'RUN_TESTS' is 'yes'.

Jenkins

stage('Release') {
  when {
    allOf {
      branch [1]
      environment name: 'RUN_TESTS', value: [2]
    }
  }
  steps {
    echo 'Releasing with tests...'
  }
}

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

A'release'

B'yes'

C'no'

D'develop'

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong branch or environment values.

Not quoting the values.

The allOf condition requires both the branch to be 'release' and the environment variable RUN_TESTS to be 'yes' for the stage to run.

5fill in blank

hard

Fill all three blanks to run the stage only when the branch is 'hotfix', the environment variable 'DEPLOY' is 'true', and the build cause is 'SCMTrigger'.

Jenkins

stage('Hotfix Deploy') {
  when {
    allOf {
      branch [1]
      environment name: 'DEPLOY', value: [2]
      triggeredBy '[3]'
    }
  }
  steps {
    echo 'Deploying hotfix...'
  }
}

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

A'hotfix'

B'true'

CSCMTrigger

D'ManualTrigger'

Attempts:

3 left

💡 Hint

Common Mistakes

Not quoting branch or environment values.

Using wrong trigger cause name.

The stage runs only if the branch is 'hotfix', the environment variable DEPLOY is 'true', and the build was triggered by SCMTrigger.

Practice

1. What is the main purpose of the when directive in a Jenkins pipeline stage?

easy

A. To set the timeout for a stage execution

B. To define environment variables for a stage

C. To specify the agent where the stage runs

D. To control whether a stage runs based on specified conditions

Solution

1. Step 1: Understand the role of when directive

   The when directive is used to decide if a stage should run or be skipped based on conditions.

2. Step 2: Compare with other stage directives

   Other directives like environment, agent, and timeout serve different purposes unrelated to conditional execution.

3. Final Answer:

   To control whether a stage runs based on specified conditions -> Option D

4. Quick Check:

   when controls stage execution [OK]

Hint: Remember: when decides if stage runs or skips [OK]

Common Mistakes:

• Confusing when with environment
• Thinking when sets agent or timeout
• Assuming when always runs the stage

2. Which of the following is the correct syntax to run a stage only on the 'main' branch using the when directive?

easy

A. when {
branch 'main'
}

B. when {
branch == 'main'
}

C. when {
if (branch == 'main')
}

D. when {
branch: 'main'
}

Solution

1. Step 1: Recall correct when syntax for branch condition

   The correct syntax uses branch 'branchName' inside when block without operators or colons.

2. Step 2: Identify syntax errors in other options

   Options B and C use invalid operators or expressions; D uses colon which is incorrect in this context.

3. Final Answer:

   when { branch 'main' } -> Option A

4. Quick Check:

   Use branch 'name' syntax [OK]

Hint: Use branch 'name' without operators in when [OK]

Common Mistakes:

• Using comparison operators inside when
• Adding colons or equal signs incorrectly
• Writing if statements inside when

3. Given the following Jenkins pipeline snippet, what will happen if the branch is 'feature'?

stage('Deploy') {
  when {
    branch 'main'
  }
  steps {
    echo 'Deploying to production'
  }
}

medium

A. The stage will run and print 'Deploying to production'

B. The stage will be skipped and nothing will print

C. The pipeline will fail with a syntax error

D. The stage will run but print nothing

Solution

1. Step 1: Understand the when condition

   The stage runs only if the branch is 'main'. Since the branch is 'feature', the condition is false.

2. Step 2: Determine stage behavior on false condition

   When when condition is false, Jenkins skips the stage and does not execute steps.

3. Final Answer:

   The stage will be skipped and nothing will print -> Option B

4. Quick Check:

   Branch mismatch skips stage [OK]

Hint: If branch doesn't match, stage is skipped silently [OK]

Common Mistakes:

• Assuming stage runs regardless of branch
• Expecting syntax error for valid when
• Thinking stage runs but steps don't print

4. Identify the error in this Jenkins pipeline stage that uses when:

stage('Test') {
  when {
    branch == 'dev'
  }
  steps {
    echo 'Running tests'
  }
}

medium

A. The stage name 'Test' is not allowed

B. Missing agent directive for the stage

C. Using '==' operator inside when is invalid syntax

D. The steps block should be inside when

Solution

1. Step 1: Check when syntax for branch condition

   The when directive expects branch 'name' without operators like '=='.

2. Step 2: Validate other parts of the stage

   Missing agent is allowed if inherited; steps must be outside when; stage name is valid.

3. Final Answer:

   Using '==' operator inside when is invalid syntax -> Option C

4. Quick Check:

   No operators in when branch condition [OK]

Hint: No operators like '==' inside when branch check [OK]

Common Mistakes:

• Using comparison operators inside when
• Placing steps inside when
• Assuming stage name restrictions

5. You want a Jenkins stage to run only when the branch is 'release' and an environment variable DEPLOY is set to 'true'. Which when directive correctly implements this?

hard

A. when {
allOf {
branch 'release'
environment name: 'DEPLOY', value: 'true'
}
}

B. when {
branch 'release' && environment name: 'DEPLOY', value: 'true'
}

C. when {
branch 'release'
environment 'DEPLOY': 'true'
}

D. when {
anyOf {
branch 'release'
environment name: 'DEPLOY', value: 'true'
}
}

Solution

1. Step 1: Understand combining conditions in when

   To require both conditions, use allOf block combining branch and environment.

2. Step 2: Analyze each option's logic

   when {
     allOf {
       branch 'release'
       environment name: 'DEPLOY', value: 'true'
     }
   }

   correctly uses allOf.

   when {
     branch 'release' && environment name: 'DEPLOY', value: 'true'
   }

   uses invalid syntax with '&&'.

   when {
     branch 'release'
     environment 'DEPLOY': 'true'
   }

   uses invalid syntax for environment condition (missing name: and value:).

   when {
     anyOf {
       branch 'release'
       environment name: 'DEPLOY', value: 'true'
     }
   }

   uses anyOf, meaning either condition suffices.

3. Final Answer:

   when { allOf { branch 'release' environment name: 'DEPLOY', value: 'true' } } -> Option A

4. Quick Check:

   Use allOf to combine multiple when conditions [OK]

Hint: Use allOf to require all conditions true [OK]

Common Mistakes:

• Using '&&' inside when block
• Using environment 'VAR': 'value' shorthand syntax
• Using anyOf when all conditions are needed