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);
}