Testing

Steps are tested with Jenkins Pipeline Unit (JPU) — a JUnit harness that loads and executes shared library steps without a running Jenkins instance.

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Running tests

./gradlew test                                    # all tests
./gradlew test --tests DetectAgentTest            # single class
./gradlew test --tests "DetectAgentTest.detects nodejs via package_json"  # single method
./gradlew clean test                              # clean first

Results: build/reports/tests/test/index.html

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How JPU works

Each test class extends BasePipelineTest. In setUp(), call super.setUp() to initialise the mock helper, then register mocks for every DSL method the step under test calls:

helper.registerAllowedMethod('fileExists', [String.class], { path -> path == 'package.json' })
helper.registerAllowedMethod('error', [String.class], { String msg -> throw new RuntimeException(msg) })
binding.setVariable('env', [MY_VAR: 'value'])

Load the step with loadScript('vars/stepName.groovy'), then invoke it:

def script = loadScript('vars/detectAgent.groovy')
assertEquals('nodejs', script.call())

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Key constraints

Java 25 + dots in method names — Groovy encodes the string literal in void 'test name'() directly as the JVM method name. Java 25 rejects names containing .. Always replace dots with underscores in test method names:

// ✗ fails on Java 25
void 'detects nodejs via package.json'() { ... }

// ✓ correct
void 'detects nodejs via package_json'() { ... }

Re-registering mocks — helper.registerAllowedMethod overwrites the previous registration for the same signature. Register a safe default in setUp(), then override per-test as needed.

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Dependencies

Library	Version	Why
com.lesfurets:jenkins-pipeline-unit	1.30	JPU test harness — published to repo.jenkins-ci.org, not Maven Central
org.codehaus.groovy:groovy-all	3.0.25	Includes ASM 9.7, required for Java 25 class file support
org.junit.jupiter:junit-jupiter	5.10.x	JUnit 5 engine