Plugin plugin = new Plugin();
        plugin.setGroupId("org.apache.maven.test.MavenExecutionPlan");
        plugin.setArtifactId("stub-plugin-" + phaseName);
        descriptor.setPlugin(plugin);
        descriptor.setArtifactId("artifact." + phaseName);
        mojoDescriptor.setPluginDescriptor(descriptor);
        mojoDescriptor.setThreadSafe(threadSafe);
        return mojoDescriptor;

    }

    public static MojoDescriptor createMojoDescriptor(Plugin plugin) {
        final PluginDescriptor descriptor = new PluginDescriptor();
        descriptor.setGroupId(plugin.getGroupId());
        descriptor.setArtifactId(plugin.getArtifactId());
        descriptor.setPlugin(plugin);
        descriptor.setVersion(plugin.getVersion());
        final MojoDescriptor mojoDescriptor = new MojoDescriptor();

    void mergeDifferentGAV() throws Exception {
        // merge implicitly assumes that merge is only called on the same GAV and does not perform any validation here!
        Metadata source = new Metadata();
        source.setArtifactId("source-artifact");
        source.setGroupId("source-group");
        source.setVersion("2.0");
        assertFalse(target.merge(source));
        assertEquals("myArtifact", target.getArtifactId());

        return plugins;
    }

    private Plugin newPlugin(String artifactId, String... goals) {
        Plugin plugin = new Plugin();

        plugin.setGroupId("org.apache.maven.plugins");
        plugin.setArtifactId(artifactId);

        for (String goal : goals) {
            PluginExecution pluginExecution = new PluginExecution();
            pluginExecution.setId("default-" + goal);
            pluginExecution.addGoal(goal);

        MavenProject project = session.getCurrentProject();

        Exclusion exclusion = new Exclusion();
        exclusion.setGroupId( "org.apache.maven.its" );
        exclusion.setArtifactId( "a" );

        new ProjectBuilder( project ).addDependency( "org.apache.maven.its", "b", "0.1", Artifact.SCOPE_RUNTIME,
                                                     exclusion );

    VersionRange getVersionRange();

    void setVersionRange(VersionRange newRange);

    void selectVersion(String version);

    void setGroupId(String groupId);

    void setArtifactId(String artifactId);

    boolean isSnapshot();

    void setResolved(boolean resolved);

    boolean isResolved();

    void setResolvedVersion(String version);

    /**
     * Sets the artifact id of the plugin.
     *
     * @param artifactId The artifact id of the plugin.
     * @return This request, never {@code null}.
     */
    PluginVersionRequest setArtifactId(String artifactId);

    /**
     * Gets the POM whose build plugins are to be scanned for the version.
     *

        }
    }

    public AttachedArtifact(Artifact parent, String type, ArtifactHandler artifactHandler) {
        this(parent, type, null, artifactHandler);
    }

    public void setArtifactId(String artifactId) {
        throw new UnsupportedOperationException(
                "Cannot change the artifactId for an attached artifact." + " It is derived from the main artifact.");
    }

        if (session != null) {
            PluginDescriptor desc = new PluginDescriptor();
            desc.setGroupId(PluginDescriptor.getDefaultPluginGroupId());
            desc.setArtifactId(PluginDescriptor.getDefaultPluginArtifactId("toolchains"));

            MavenProject current = session.getCurrentProject();

            if (current != null) {
                // TODO why is this using the context

    }

    protected static Metadata createMetadata(Artifact artifact, Versioning versioning) {
        Metadata metadata = new Metadata();
        metadata.setGroupId(artifact.getGroupId());
        metadata.setArtifactId(artifact.getArtifactId());
        metadata.setVersion(artifact.getVersion());
        metadata.setVersioning(versioning);
        return metadata;
    }