@Test
public void addProvider() throws Exception {

    SingleGroupAddressHolder addressHolder = new SingleGroupAddressHolder(null);
    addressHolder.addProvider(new ProviderGroup("xxx", new ArrayList<ProviderInfo>()));
    Assert.assertTrue(addressHolder.getProviderGroup(ADDRESS_DEFAULT_GROUP).size() == 0);
    addressHolder.addProvider(new ProviderGroup("xxx", Arrays.asList(
        ProviderHelper.toProviderInfo("127.0.0.1:12200"),
        ProviderHelper.toProviderInfo("127.0.0.1:12201"))));
    Assert.assertTrue(addressHolder.getProviderGroup(ADDRESS_DEFAULT_GROUP).size() == 2);
    addressHolder.addProvider(new ProviderGroup(ADDRESS_DIRECT_GROUP, new ArrayList<ProviderInfo>()));
    Assert.assertTrue(addressHolder.getProviderGroup(ADDRESS_DIRECT_GROUP).size() == 0);
    addressHolder.addProvider(new ProviderGroup(ADDRESS_DIRECT_GROUP,
        Arrays.asList(ProviderHelper.toProviderInfo("127.0.0.1:12200"),
            ProviderHelper.toProviderInfo("127.0.0.1:12201"))));
    Assert.assertTrue(addressHolder.getProviderGroup(ADDRESS_DIRECT_GROUP).size() == 2);
}