Unit Testing Maven Mojo - Components and parameters are null

Question

Based on the documentation and mailing threads I have seen 3 ways to inject the maven project into my mojo:

/**
  * Project instance
  * 
  * @parameter default-value="${project}"
  * @required
  * @readonly
  */
private MavenProject project;


@Component
private MavenProject project;


@Parameter(  expression = "${project}" )    
private MavenProject project;

But regardless of which one of these I choose, when I run the unit test based on the example I found in maven docs, project is always null.

public void testMojoGoal() throws Exception {
    File testPom = new File(getBasedir(),
            "src/test/resources/unit/basic-test/sample-sh-project-config.xml");

    ShunitResourcesMojo mojo = (ShunitResourcesMojo) lookupMojo("prepare",testPom);

    assertNotNull(mojo);

    mojo.execute();     
}

mojo execute contains (and fails on)

Validate.notNull(project);

Answer 1

I was just working on my own plugin and ran into the same problem. I could not find documentation on it, but I had a look at the maven-ant-plugin (https://svn.apache.org/repos/asf/maven/plugins/trunk/maven-ant-plugin) to see how they did it.

I assume this is built-in test harness behavior, but you have to add a "project" parameter to your test pom.xml to set the value to a subclass of MavenProjectStub, for example in the "ant-test" test:

  <plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-ant-plugin</artifactId>
    <configuration>
      <project implementation="org.apache.maven.plugin.ant.stubs.AntTestMavenProjectStub"/>
      <settings implementation="org.apache.maven.plugin.ant.stubs.SettingsStub"/>
      <localRepository>${localRepository}</localRepository>
    </configuration>
  </plugin>

I hope you had your answer already, just posting for those to follow.