@Test
public void login() throws Exception {

    TestSubscriber<Boolean> subscriber = TestSubscriber.create();
    // Success to login
    userDataSource.login("Nolan1995", "a123456").subscribe(subscriber);
    subscriber.assertValue(true);
    subscriber = TestSubscriber.create();
    // Fail to login, may be bug in TestSubscriber
    userDataSource.login("Nolan1995", "").subscribe(subscriber);
    subscriber.assertNoValues();
}