如何测试使用回调的函数?

Question

假设我们有一个回调函数的接口:

public interface Model {
interface UserListener {
void callback(User user);
}
void getUser(String username, UserListener listener);
}

我们有一个方法来调用作为参数给出的回调:

public class Presenter() {
...
public Presenter(Model model, View view) {
this.model = model;
this.view = view;
}
public void checkLogin() {
String username = view.getUsername();
String password = view.getPassword();
model.getUser(username, user -> {
if (user == null) {
view.loginFailed();
} else {
view.loginSuccess(user.getName());
}
});
}
}

我希望沿着下面的行来测试它:

when(view.getUsername()).thenReturn("abc");
when(view.getPassword()).thenReturn("xyz");
Presenter presenter = new Presenter(view, model);
presenter.checkLogin();
// How do I verify that view.loginFailed() or view.loginSuccess() is called here
...

现在，问题:给定这种场景，如何测试(Mockito)调用了loginFailed()和loginSuccess()的视图?

Answer 1

在Mockito中，当对mock的调用需要做的不仅仅是返回值时，您可以使用Answer:

@ExtendWith(MockitoExtension.class)
public class MockEg {
public interface Model {
interface UserListener {
void callback(User user);
}
void getUser(String username, UserListener listener);
}
interface User {}
@Test
public void aTest() {
Model model = mock(Model.class);
User user = mock(User.class);
doAnswer(new Answer<Void>() {
@Override
public Void answer(InvocationOnMock invocation) throws Throwable {
Model.UserListener listener = invocation.getArgument(1);
listener.callback(user);
return null;
}
}).when(model).getUser(any(), any());
...
}
}