@Test
public void testAlwaysChooseAvailableServer() throws TException {

    ServerSelector serverSelector = new ServerSelector(
            "appId", Arrays.asList(AVAILABLE_INSTANCE_1, NO_AVAILABLE_INSTANCE_1), "dasClientVersion", "ppdaiClientVersion", "clientAddress"
    );
    for (int i = 0 ;i < 100; i++){
        DasResult response = serverSelector.execute(REQUEST);
        Assert.assertNotNull(response);
    }
}