Design and provide unit tests to cover more use cases.
@Test
    public void testRecover() throws Exception {
        
        abstractRegistry.recover();
        Assert.assertFalse(abstractRegistry.getRegistered().contains(testUrl));
        Assert.assertNull(abstractRegistry.getSubscribed().get(testUrl));
        
        abstractRegistry.register(testUrl);
        abstractRegistry.subscribe(testUrl, listener);
        abstractRegistry.recover();
        
        Assert.assertTrue(abstractRegistry.getRegistered().contains(testUrl));
        Assert.assertNotNull(abstractRegistry.getSubscribed().get(testUrl));
        Assert.assertTrue(abstractRegistry.getSubscribed().get(testUrl).contains(listener));
    }
    @Test
    public void testRecover2() throws Exception {
        List<URL> list = getList();
        abstractRegistry.recover();
        Assert.assertEquals(0, abstractRegistry.getRegistered().size());
        for (URL url : list) {
            abstractRegistry.register(url);
        }
        Assert.assertEquals(3, abstractRegistry.getRegistered().size());
        abstractRegistry.recover();
        Assert.assertEquals(3, abstractRegistry.getRegistered().size());
    }
    /**
     * Test method for
     * {@link org.apache.dubbo.registry.support.AbstractRegistry#notify(List)}.