Mocked MavenProject used in InjectMojo is rather unsafe to use

[elmuerte]

Affected version

3.4.0

Bug description

The mocked maven project created when using @InjectMojo is quite unsafe, only the properties are usable.

maven-plugin-testing/maven-plugin-testing-harness/src/main/java/org/apache/maven/api/plugin/testing/MojoExtension.java

Lines 294 to 298 in 3d28d1e

	private MavenProject mockMavenProject() {
	MavenProject mavenProject = Mockito.mock(MavenProject.class);
	lenient().when(mavenProject.getProperties()).thenReturn(new Properties());
	return mavenProject;
	}

Everything else would return null. This is not documented and thus results in surprises during test executions like an NPE when in the mojo when you do project.getBuild().getDirectory() to get the target directory.

You can work around this like this:

    @Inject
    MavenProject project;

    @BeforeEach
    @Basedir("target/test-classes/projects/run")
    @InjectMojo(goal = "findings")
    void setUp(FindingsMojo findingsMojo) {
        when(project.getBuild()).thenReturn(mock());
        when(project.getBuild().getDirectory()).thenReturn("target/test-classes/projects/run/target");
    }

It would be nicer if parts of the project would have more safe to use defaults. But it should be at least documented that basic mocks are being inserted into the resolved mojos.

In the Javadoc for MojoExtension it also hints that certain properties are resolved

@MojoParameter(name = "outputDirectory", value = "${project.build.directory}/generated")

But that does not happen at all.

[elmuerte]

Also the mojo which has default settings values based on properties are not initialized based on the content of the provided POM.

[mjog]

I'm not too concerned about a mock project being a blank state (this is what mocks are), but if a POM is specified using @InjectMojo(pom="…", …) then I really would expect the project to be initialised according to all Maven defaults, and the contents of the given file.