Design and provide unit tests to cover more use cases.
abstractRegistry.getRegistered().clear();
        List<URL> urlList = getList();
        for (URL url : urlList) {
            abstractRegistry.register(url);
        }
        Assert.assertThat(abstractRegistry.getRegistered().size(), Matchers.equalTo(urlList.size()));
    }
    @Test(expected = IllegalArgumentException.class)
    public void testRegisterIfURLNULL() throws Exception {
        abstractRegistry.register(null);
        Assert.fail("register url == null");
    }
    /**
     * Test method for
     * {@link org.apache.dubbo.registry.support.AbstractRegistry#unregister(URL)}.
     *
     * @throws Exception
     */
    @Test
    public void testUnregister() throws Exception {
        
        URL url = new URL("dubbo", "192.168.0.1", 2200);
        abstractRegistry.getRegistered().add(url);
        abstractRegistry.unregister(url);
        Assert.assertThat(false, Matchers.equalTo(abstractRegistry.getRegistered().contains(url)));
        
        abstractRegistry.getRegistered().clear();
        List<URL> urlList = getList();
        for (URL urlSub : urlList) {
            abstractRegistry.getRegistered().add(urlSub);