public void EnsureGenerateHashInvokesCryptoServiceComputeOperation()
        {
            var cryptoService = A.Fake <ICryptoService>();

            var service = new PasswordEncryptor(cryptoService);

            const string salt     = "salt";
            const string password = "******";

            service.GenerateHash(password, salt);

            A.CallTo(() => cryptoService.Compute(password, salt))
            .MustHaveHappened(Repeated.Exactly.Once);
        }