// -----------/
    // - Methods -/
    // -----------/

    /**
     * Method addExtension.
     *
     * @param coreExtension a coreExtension object.
     */
    public void addExtension(CoreExtension coreExtension) {
        getExtensions().add(coreExtension);
    } // -- void addExtension( CoreExtension )

    /**
     * Method getExtensions.
     *
     * @return List
     */

        Build build = project.getModel().getBuild();

        Extension extension = createExtension("other.group", "other-artifact", "1.0");

        build.addExtension(extension);

        new ProjectSorter(Collections.singletonList(project));
    }

    @Test
    void testMatchingArtifactIdsDifferentGroupIds() throws Exception {