LoginPresenterTest.java

public class LoginPresenterTest {
  private TestLoginController loginController = new TestLoginController();
  private LoginPresenter loginPresenter = new LoginPresenter(new TestAccountValidator());

  @Before public void setUp() throws Exception {
    loginPresenter.register(loginController);
  }

  @Test public void onLoginButtonClick_shouldShowSuccessOnValidInput() throws Exception {
    loginPresenter.onLoginButtonClick("valid_username", "valid_password");
    assertThat(loginController.success).isTrue();
  }

  @Test public void onLoginButtonClick_shouldShowErrorOnInvalidInput() throws Exception {
    loginPresenter.onLoginButtonClick("invalid_username", "invalid_password");
    assertThat(loginController.error).isTrue();
  }
}