@Test
public void getProviders() throws Exception {

    SingleGroupAddressHolder addressHolder = new SingleGroupAddressHolder(null);
    Assert.assertTrue(ProviderHelper.isEmpty(addressHolder.getProviderGroup(null)));
    Assert.assertTrue(ProviderHelper.isEmpty(addressHolder.getProviderGroup(StringUtils.EMPTY)));
    Assert.assertTrue(ProviderHelper.isEmpty(addressHolder.getProviderGroup(ADDRESS_DEFAULT_GROUP)));
    addressHolder.registryGroup.add(ProviderHelper.toProviderInfo("127.0.0.1:12200"));
    addressHolder.registryGroup.add(ProviderHelper.toProviderInfo("127.0.0.1:12201"));
    Assert.assertTrue(addressHolder.getProviderGroup(null).size() == 2);
    Assert.assertTrue(addressHolder.getProviderGroup(StringUtils.EMPTY).size() == 2);
    Assert.assertTrue(addressHolder.getProviderGroup(ADDRESS_DEFAULT_GROUP).size() == 2);
    addressHolder.directUrlGroup.add(ProviderHelper.toProviderInfo("127.0.0.1:12200"));
    Assert.assertTrue(addressHolder.getProviderGroup(ADDRESS_DIRECT_GROUP).size() == 1);
    Assert.assertTrue(addressHolder.getProviderGroup(null).size() == 2);
    Assert.assertTrue(addressHolder.getProviderGroup(StringUtils.EMPTY).size() == 2);
    Assert.assertTrue(addressHolder.getProviderGroup(ADDRESS_DEFAULT_GROUP).size() == 2);
}