public void CanEnrollACustomer() { //Arrange FakeCustomerValidator validation = new FakeCustomerValidator(); FakeCreditCheckValidator creditCheck = new FakeCreditCheckValidator(); FakeCustomerRepository repository= new FakeCustomerRepository(); var sut = new CustomerService(validation, creditCheck, repository); Customer customer = new Customer(); //Act sut.EnrollCustomer(customer); //Assert Assert.That(validation.WasCalled); Assert.That(creditCheck.WasCalled); Assert.That(repository.WasCalled); }