Add unit test to the modules: 
dubbo-registry/dubbo-registry-multicast
   dubbo-registry/dubbo-registry-redis
  dubbo-registry/dubbo-registry-zookeeper 
@Test(expected = IllegalStateException.class)
    public void testAnyHost() {
        URL errorUrl = URL.valueOf("multicast://0.0.0.0/");
        new MulticastRegistry(errorUrl);
    }
    @Test
    public void testGetCustomPort() {
        URL customPortUrl = URL.valueOf("multicast://239.255.255.255:4321/");
        MulticastRegistry multicastRegistry = new MulticastRegistry(customPortUrl);
        assertThat(multicastRegistry.getUrl().getPort(), is(4321));
    }
    /**
     * Test method for {@link com.alibaba.dubbo.registry.multicast.MulticastRegistry#getRegistered()}.
     */
    @Test
    public void testRegister() {
        Set<URL> registered = null;
        
        registered = registry.getRegistered();
        for (int i = 0; i < 2; i++) {
            registry.register(serviceUrl);
            registered = registry.getRegistered();
            assertTrue(registered.contains(serviceUrl));
        }
        
        registered = registry.getRegistered();
        assertEquals(1, registered.size());
    }
    /**
     * Test method for