private final ListProperty<String> includeXpack;

        XpackRestResourcesSpec(ObjectFactory objects) {
            includeCore = objects.listProperty(String.class);
            includeXpack = objects.listProperty(String.class);
        }

        public void includeCore(String... include) {
            this.includeCore.addAll(include);
        }

        public void includeXpack(String... include) {

 * restResources {
 *   restApi {
 *     includeCore 'index', 'cat'
 *     includeXpack 'enrich'
 *   }
 * }
 * </pre>
 * <br>
 * <strong>Rest YAML tests :</strong> <br>
 * When the {@link RestResourcesPlugin} has been applied the {@link CopyRestTestsTask} will copy the Rest YAML tests if explicitly
 * configured with `includeCore` or `includeXpack` through the `restResources.restTests` extension.
 * <i>For example:</i>
 * <pre>

    }

    @SkipWhenEmpty
    @InputFiles
    public FileTree getInputDir() {
        FileTree coreFileTree = null;
        FileTree xpackFileTree = null;
        if (includeXpack.get().isEmpty() == false) {
            xpackPatternSet.setIncludes(includeXpack.get().stream().map(prefix -> prefix + "*/**").collect(Collectors.toList()));
            xpackFileTree = xpackConfigToFileTree.apply(xpackConfig).matching(xpackPatternSet);
        }

            apply plugin: 'elasticsearch.java'
            apply plugin: 'elasticsearch.rest-resources'

            restResources {
                restTests {
                    includeCore 'foo'
                    includeXpack 'bar'
                }
            }
        """
        String apiCore1 = "foo1.json"
        String apiCore2 = "foo2.json"
        String apiXpack = "xpack.json"
        String coreTest = "foo/10_basic.yml"