Mocking Cache Manage for Active Objects Test

I am creating a test for Active Objects. My service implementation depends on Active Object and CacheManage objects as shown below.

    @Before
    public void setUp() throws Exception {
        assertNotNull(entityManager);

        ao = new TestActiveObjects(entityManager);
        projectService = new ProjectServiceImpl(ao, cacheManager);  //how to initialize?
    }

How do I create test for such service implementation? My service methods depends on cache. Is there any mock cache manager available?