Testing Complex Mojo Parameters

Note: This example improves the cookbook for testing complex Mojo parameters.

In real plugin development, you will use specific Maven objects like MavenProject, MavenSession, MavenSettings and so on.

Provided mocks and stubs

The Maven Plugin Testing Harness provides mocks and stubs for the following Maven objects. For creating mocks Mockito framework is used.

MavenSession

There is provided a mock for MavenSession with basic configuration:

session#getUserProperties and session#getSystemProperties empty Properties objects.
session#getCurrentProject - a current prepared MavenProject
session#getLocalRepository - equals to request#getLocalRepository
session#getRequest returns a spy for DefaultMavenExecutionRequest with configuration
- request#getStartTime - celling time
- request#getBaseDirectory() - current base directory
- request#getUserProperties, request#getSystemProperties - copy of MavenSession properties
- request#getLocalRepository, request#getLocalRepositoryPath - point to local repository in ${basedir}/target/local-repo
- request#getRemoteRepositories, request#getPluginArtifactRepositories - default remote repositories for Maven Central

If @MojoTest(realRepositorySession = true) is used, then session#getRepositorySession returns a real RepositorySystemSession configured with local repository in ${basedir}/target/local-repo and default remote repositories for Maven Central.

MavenProject

There is provided a spy for MavenProject with basic configuration:

project#getBasedir - current base directory
project#getCompileSourceRoots - ${basedir}/src/main/java
project#getTestCompileSourceRoots - ${basedir}/src/test/java
project#getBuild - a spy for Build with configuration
- build#getDirectory - ${basedir}/target
- build#getOutputDirectory - ${basedir}/target/classes
- build#getTestOutputDirectory - ${basedir}/target/test-classes
- build#getSourceDirectory - ${basedir}/src/main/java
- build#getTestSourceDirectory - ${basedir}/src/test/java
- build#getResources - ${basedir}/src/main/resources
- build#getTestResources - ${basedir}/src/test/resources

If @MojoTest(realRepositorySession = true) is used, then project#getRemote*Repositories returns default remote repositories for Maven Central.

MojoExecution

There is provided a spy for MojoExecution with current plugin Mojo descriptor.

Plugin logger

There is provided a spy for Slf4j wrapper of org.apache.maven.plugin.logging.Log interface. You can verify log messages using Mockito verifications.

Create custom Stubs for Maven objects

You can create your own stubs for Maven objects by define them in plugin test.

If you provide your own stub for a Maven object, then it will be used instead of the default provided one.

import javax.inject.Inject;

import org.apache.maven.api.di.Provides;
import org.apache.maven.api.plugin.testing.InjectMojo;
import org.apache.maven.execution.MavenSession;
import org.apache.maven.plugin.logging.Log;
import org.apache.maven.project.MavenProject;
import org.apache.maven.settings.Settings;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Nested;
import org.junit.jupiter.api.Test;
import org.mockito.Mockito;

@MojoTest
class MyMojoTest {

    // define your stub for MavenProject
    @Provides
    MavenProject stubProject() {
        // return your stub implementation
        return new MavenProjectStub();
    }

    @Provides
    MavenSession stubSession() {
        // return your stub implementation
        return new MyMavenSessionStub();
    }

    // inject the stubbed or default MavenSession
    @Inject
    private MavenSession session;

    @Inject
    private Log log;
    
    @BeforeEach

    void setup() {
        // customize injected stubs or mocks
        Mockito.when(session.getSettings()).thenReturn(new MySettingsStub());
    }

    @Test
    @InjectMojo(goal = "my-goal")
    void myMojoTest(MyMojo mojo) {
        mojo.execute();
        // your verifications, eg
        Mockito.verify(log).info("My info log message");
    }

    // you can also group stubs in nested test classes
    @Nested
    class NestedTest {

        // define your stub for MavenProject in nested class
        @Provides
        MavenProject stubProject() {
            // return your stub implementation
            return new MavenProjectStub2();
        }

        @BeforeEach
        void setup() {
            // customize injected stubs or mocks for this nested class
            Mockito.when(session.getSettings()).thenReturn(new MySettingsStub());
        }

        @Test
        @InjectMojo(goal = "my-goal")
        void myMojoTest(MyMojo mojo) {
            mojo.execute();
            // your verifications
        }
    }
}