public ProjectBuildingRequest getProjectBuildingRequest() {
        return request.getProjectBuildingRequest().setRepositorySession(getRepositorySession());
    }

    public List<String> getPluginGroups() {
        return request.getPluginGroups();
    }

    public boolean isOffline() {
        return request.isOffline();
    }

    public MavenProject getTopLevelProject() {
        return topLevelProject;
    }

        }

        return this;
    }

    @Override
    public MavenExecutionRequest addPluginGroup(String pluginGroup) {
        if (!getPluginGroups().contains(pluginGroup)) {
            getPluginGroups().add(pluginGroup);
        }

        return this;
    }

    @Override
    public MavenExecutionRequest addPluginGroups(List<String> pluginGroups) {

                .pluginGroups(Arrays.asList("org.codehaus.plexus"))
                .build();

        Settings merged = SettingsUtilsV4.merge(dominant, recessive);

        List<String> pluginGroups = merged.getPluginGroups();

        assertNotNull(pluginGroups);
        assertEquals(3, pluginGroups.size());
        assertEquals("org.apache.maven.plugins", pluginGroups.get(0));

                    "usePluginRegistry",
                    null,
                    "is deprecated and has no effect.");
        }

        List<String> pluginGroups = settings.getPluginGroups();

        if (pluginGroups != null) {
            for (int i = 0; i < pluginGroups.size(); i++) {
                String pluginGroup = pluginGroups.get(i);