public void Failure_Ok() { var error = "error message"; var success = new Failure <object, string>(error); var successCalled = false; var failureCalled = false; success.Do( onSuccess: o => { successCalled = true; }, onFailure: err => { failureCalled = true; }); Assert.That(successCalled, Is.False); Assert.That(failureCalled, Is.True); }