@Test
public void size() throws Exception {

    ProviderGroup pg = new ProviderGroup("xxx", null);
    Assert.assertTrue(pg.size() == 0);
    pg = new ProviderGroup("xxx", new ArrayList<ProviderInfo>());
    Assert.assertTrue(pg.size() == 0);
    pg = new ProviderGroup("xxx", Arrays.asList(ProviderHelper.toProviderInfo("127.0.0.1:12200")));
    Assert.assertTrue(pg.size() == 1);
}