public void AuthorizeReturnsUniqueId() { //Arrange _authRequest = new AuthorizeRequest() { CardNumber = "5105105105105100", Currency = "GBP", Amount = 20 }; var authId = "123-456"; _mockLuhnCheckService.Setup(m => m.IsValidCardNumber(It.IsAny <string>())).Returns(true); _mockRepo.Setup(a => a.Authorize(It.IsAny <AuthorizeRequest>())).Returns(authId); //Act var authResponse = _authService.AuthorizeTransaction(_authRequest); //Assert Assert.AreEqual(authId, authResponse.AuthorizationId); }