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C# unit testing MassTransit handler with MSTest, Moq and FluentAssertions. Can't verify method called exactly once

I have this class called Handler, which is a MassTransit IConsumer:
public class Handler : IConsumer<ICommand>
{
private readonly IOrderRepository _orderRepository;
public Handler(IOrderRepository orderRepository)
{
_orderRepository = orderRepository ?? throw new ArgumentNullException(nameof(orderRepository));
}
public async Task Consume(ConsumeContext<ICommand> context)
{
var command = context.Message;
var orderId = new OrderId(command.OrderId);
var order = await _orderRepository.FindOrderAsync(orderId, context.CancellationToken);
if (order is null)
{
await context.RespondAsync(CommandResponse.NotFound);
return;
}
order.Cancel();
await _orderRepository.SaveOrderAsync(order, context.CancellationToken);
await context.RespondAsync(CommandResponse.Submitted);
}
}
I have two unit tests for it. Here's the one that seems to work fine:
[TestMethod]
public async Task Consume_WithExistingOrderId_CancelsOrderAndSavesChangesAndReturnsSubmitted()
{
// Arrange
var mockConsumer = new Mock<IConsumer<ICommand>>();
var mockRepository = new Mock<IOrderRepository>();
var sut = new Handler(mockRepository.Object);
var mockCommand = new Mock<ICommand>();
var mockContext = new Mock<ConsumeContext<ICommand>>();
mockContext.Setup(x => x.Message).Returns(mockCommand.Object);
mockContext.Setup(x => x.RespondAsync(It.IsAny<CommandResponse>())).Returns(Task.CompletedTask);
var existingOrderId = new OrderId(Guid.NewGuid());
mockCommand.Setup(x => x.OrderId).Returns(existingOrderId.Value);
var order = GetTestOrder(existingOrderId);
mockRepository.Setup(x => x.FindOrderAsync(existingOrderId, It.IsAny<CancellationToken>())).ReturnsAsync(order);
// Act
await sut.Consume(mockContext.Object);
// Assert
mockRepository.Verify(x => x.SaveOrderAsync(order, It.IsAny<CancellationToken>()), Times.Once());
mockContext.Verify(x => x.RespondAsync(CommandResponse.Submitted), Times.Once());
order.IsCancelled.Should().BeTrue();
}
And here's the one that isn't doing what I expected:
[TestMethod()]
public async Task Consume_WithNonExistantOrderId_ReturnsNotFoundResponseAndDoesNotSave()
{
// Arrange
var mockRepository = new Mock<IOrderRepository>();
var sut = new Handler(mockRepository.Object);
var mockCommand = new Mock<ICommand>();
var mockContext = new Mock<ConsumeContext<ICommand>>();
mockContext.Setup(x => x.Message).Returns(mockCommand.Object);
mockContext.Setup(x => x.RespondAsync(It.IsAny<CommandResponse>())).Returns(Task.CompletedTask);
var nonExistantOrderId = new OrderId(Guid.NewGuid());
mockCommand.Setup(x => x.OrderId).Returns(nonExistantOrderId.Value);
mockRepository.Setup(x => x.FindOrderAsync(nonExistantOrderId, It.IsAny<CancellationToken>())).ReturnsAsync((Order?)null);
// Act
await sut.Consume(mockContext.Object);
// Assert
mockRepository.Verify(x => x.SaveOrderAsync(It.IsAny<Order>(), It.IsAny<CancellationToken>()), Times.Never());
mockContext.Verify(x => x.RespondAsync(CommandResponse.NotFound), Times.Once());
}
Both unit tests require that the Handler calls the RespondAsync method of the MassTransit context exactly once. However, the second unit test doesn't pass, saying that the method was never called. I don't see why it was never called. When I debug into the method it appears to show the method is called.
I can't tell if my test is wrong or if my system under test is wrong. Can anybody see the problem please?
(Also, if anybody can see how to make my code more testable and my unit tests shorter and simpler that would also be appreciated.)

The problem is with the nonExistantOrderId and using that for the match in expectation.
mockRepository
.Setup(x => x.FindOrderAsync(nonExistantOrderId, It.IsAny<CancellationToken>()))
.ReturnsAsync((Order?)null);
the mock expects to get that specific instance when the subject is being exercised but the subject initialized its own instance which causes the mock to not invoke the async call and exit the subject before that target line can be invoked.
This is why
mockRepository.Verify(x => x.SaveOrderAsync(It.IsAny<Order>(), It.IsAny<CancellationToken>()), Times.Never());
supposedly passed verification, and
mockContext.Verify(x => x.RespondAsync(CommandResponse.NotFound), Times.Once());
failed since the subject code exited before reaching both members that are the targets of your verification.
Loosen the match using It.IsAny<OrderId>()
mockRepository
.Setup(x => x.FindOrderAsync(It.IsAny<OrderId>(), It.IsAny<CancellationToken>()))
.ReturnsAsync((Order?)null);
so that the mocked async call can be invoked and allow the code to flow to completion.

I have accepted Nkosi's answer because it solved the problem stated in the question. Thank you, Nkosi.
However, the resources that were provided by the MassTransit boss-man, #Chris Patterson, were helpful in making a better unit test altogether. That's why I'm posting this alternative answer. This answer rewrites the original unit test to use the MassTransit test harness, and I hope it helps somebody one day.
Chris's links have somehow disappeared from sight. However, I think he posted this:
https://www.youtube.com/watch?v=Cx-Mc0DCpfE&t=545s
And this:
https://masstransit-project.com/usage/testing.html
The rewritten method:
public interface ICommand
{
Guid OrderId { get; }
}
public record Command : ICommand
{
public Command(Guid orderId)
{
OrderId = orderId;
}
public Guid OrderId { get; }
}
public class Handler : IConsumer<ICommand>
{
private readonly IOrderRepository _orderRepository;
public Handler(IOrderRepository orderRepository)
{
_orderRepository = orderRepository ?? throw new ArgumentNullException(nameof(orderRepository));
}
public async Task Consume(ConsumeContext<ICommand> context)
{
var command = context.Message;
OrderId orderId = new OrderId(command.OrderId);
var order = await _orderRepository.FindOrderAsync(orderId, context.CancellationToken);
if (order is null)
{
await context.RespondAsync(CommandResponse.NotFound);
return;
}
order.Cancel();
await _orderRepository.SaveOrderAsync(order, context.CancellationToken);
await context.RespondAsync(CommandResponse.Submitted);
}
}
The rewritten unit test class:
[TestClass()]
public class Handler_Tests
{
private static OrderId ExistingOrderId = new OrderId("d94108e4-1121-401a-a6ef-c7736054041d");
private static OrderId NonExistentOrderId = new OrderId("daaa72a0-8f8c-4a9b-b4ad-ebefbb6b5aa2");
private static CustomerId ExistingCustomerId = new CustomerId("5fbf40d8-c064-4821-8948-a520863e6242");
[TestMethod()]
public async Task Consume_WithExistingOrderId_CancelsOrderAndSavesChangesAndReturnsSubmitted2()
{
// Arrange
var harness = new InMemoryTestHarness();
var mockRepository = GetMockOrderRepository();
var sut = harness.Consumer(() =>
{
return new Handler(mockRepository.Object);
});
await harness.Start();
try
{
var requestClient = await harness.ConnectRequestClient<ICommand>();
var command = new Command(ExistingOrderId.Value);
// Act
var response = await requestClient.GetResponse<CommandResponse>(command, It.IsAny<CancellationToken>());
// Assert
mockRepository.Verify(x => x.SaveOrderAsync(It.IsAny<Order>(), It.IsAny<CancellationToken>()), Times.Once());
response.Message.Result.Should().Be(CommandResponse.Results.Submitted);
}
finally
{
await harness.Stop();
}
}
[TestMethod()]
public async Task Consume_WithNonExistentOrderId_ReturnsNotFoundResponseAndDoesNotSave()
{
// Arrange
var harness = new InMemoryTestHarness();
var mockRepository = GetMockOrderRepository();
var sut = harness.Consumer(() =>
{
return new Handler(mockRepository.Object);
});
await harness.Start();
try
{
var requestClient = await harness.ConnectRequestClient<ICommand>();
var command = new Command(NonExistentOrderId.Value);
var response = await requestClient.GetResponse<CommandResponse>(command, It.IsAny<CancellationToken>());
mockRepository.Verify(x => x.SaveOrderAsync(It.IsAny<Order>(), It.IsAny<CancellationToken>()), Times.Never());
response.Message.Result.Should().Be(CommandResponse.Results.NotFound);
}
finally
{
await harness.Stop();
}
}
private static Order GetTestOrder(OrderId orderId)
{
var orderItem = GetTestOrderItem();
return Order.Place(orderId, ExistingCustomerId, new[] { orderItem });
}
private static OrderItem GetTestOrderItem()
{
var productId = new ProductId(Guid.NewGuid());
var price = new Price(1, PurchaseCurrency.Usd);
var quantity = new Quantity(1, UnitOfMeasure.Each);
return new OrderItem(productId, quantity, price);
}
private static Mock<IOrderRepository> GetMockOrderRepository()
{
var mockRepository = new Mock<IOrderRepository>();
mockRepository.Setup(x => x.FindOrderAsync(It.IsAny<OrderId>(), It.IsAny<CancellationToken>()))
.ThrowsAsync(new InvalidOperationException(
$"This mock is set up to work with {nameof(ExistingOrderId)} and {nameof(NonExistentOrderId)}."));
mockRepository.Setup(x => x.FindOrderAsync(ExistingOrderId, It.IsAny<CancellationToken>()))
.ReturnsAsync(GetTestOrder(ExistingOrderId));
mockRepository.Setup(x => x.FindOrderAsync(NonExistentOrderId, It.IsAny<CancellationToken>()))
.ReturnsAsync((Order?)null);
return mockRepository;
}
}

I want to write a test that will definitely tell if the mock-method was called

I have a method:
public class CreateNewAccountUseCase
{
private readonly IAccountRepository _accountRepository;
public CreateNewAccountUseCase(IAccountRepository accountRepository)
{
_accountRepository = accountRepository;
}
public virtual async Task Execute(Account account)
{
await _accountRepository.Create(account);
}
}
I use it in the controller:
public async Task<ActionResult<AccountModel>> CreateAccount([FromBody]CreatingAccount creatingAccount)
{
var account = creatingAccount.ConvertToAccount();
await _createNewAccountUseCase.Execute(account);
return Created($"/accounts/{account.Id}", account);
}
I want to be sure that the UseCase method will be exactly called.
I wrote this controller test:
[Fact]
public async Task Create()
{
// arrange
var account = new CreatingAccount();
var accountRepository = new Mock<IAccountRepository>();
var createNewAccountUseCase = new Mock<CreateNewAccountUseCase>(accountRepository.Object);
createNewAccountUseCase.Setup(m => m.Execute(account)).Returns(Task.CompletedTask);
// act
await controller.CreateAccount(account);
// assert
createNewAccountUseCase.Verify(m => m.Execute(account), Times.Once);
}
I expect createNewAccountUseCase.Verify() to check if the method has been method but I get failed test with a message:
Moq.MockException :
Expected invocation on the mock once, but was 0 times: m => m.Execute(account)
Performed invocations:
Mock<CreateNewAccountUseCase:1> (m):
No invocations performed.
How do I make sure the method (createNewAccountUseCase.Verify()) is called?

You are mocking the subject under test. Instead mock the dependency and invoked the method under test
[Fact]
public async Task Create() {
// arrange
var account = new CreatingAccount();
var accountRepository = new Mock<IAccountRepository>();
accountRepository.Setup(m => m.Create(It.IsAny<Account>())).Returns(Task.CompletedTask);
var createNewAccountUseCase = new CreateNewAccountUseCase(accountRepository.Object);
// act
await createNewAccountUseCase.Execute(account.ConvertToAccount());
// assert
accountRepository.Verify(m => m.Create(It.IsAny<Account>()), Times.Once);
}
The assertion can then be done on the repository mock to verify that the method behaves as expected.
In the controller test of your question you could have used the mock use case but your also need to make sure that it was injected into the controller.
But your example showed no such injection.
The following example creates the controller and explicitly injects the dependency
[Fact]
public async Task Create() {
// arrange
var account = new CreatingAccount();
var accountRepository = new Mock<IAccountRepository>();
accountRepository.Setup(m => m.Create(It.IsAny<Account>())).Returns(Task.CompletedTask);
var createNewAccountUseCase = new CreateNewAccountUseCase(accountRepository.Object);
var controller = new MyController(createNewAccountUseCase);
// act
await controller.CreateAccount(account);
// assert
accountRepository.Verify(m => m.Create(It.IsAny<Account>()), Times.Once);
}

Getting exception with Moq when trying to test Task

I'm trying to use Moq (4.10) on async calls but I cannot get the hang of it.
Search on how to do so and found answers which I've tried but I cannot make it to work .
This is my test
public class Test
{
[Fact]
public void Test_Create()
{
var repositoryMock = new Mock<IRepository>();
repositoryMock
.Setup(repo => repo.CreateAsync(It.IsAny<Aggregate >()))
.Returns(Task.CompletedTask);
/// also tried this
/// => .Returns(Task.FromResult(default(object)))
/// and
/// => .Returns(Task.FromResult(false)));
var useCase = new CreateUseCase(repositoryMock.Object);
Task.Run(async () => { await useCase.HandleAsync(new CreateRequest()); });
repositoryMock.VerifyAll();
}
}
resources
How can I tell Moq to return a Task?
Getting this exception
Moq.MockException: 'The following setups on mock
'Mock<.Repository.IRepository:00000001>' were not matched: IRepository
repo => repo.CreateAsync(It.IsAny < Aggregate>())
The repo looks like this
public interface IRepository
{
Task CreateAsync(Aggregate aggregate);
}
The UseCase
public class CreateUseCase : IUseCaseHandler<CreatRequest>
{
private IRepository _repository;
public CreateUseCase (IRepository repository)
{
_repository= repository?? throw new System.ArgumentNullException(nameof(repository));
}
public async Task HandleAsync(CreateRequest request, CancellationToken? cancellationToken = null)
{
Aggregate aggregate = new Aggregate();
aggregate.Create();
await _repository.CreateAsync(aggregate);
}
}
The Repository
public sealed class OrderRepository : ProxyRepository<OrderAggregate>, IOrderRepository
{
public OrderRepository(IUnitOfWork unitOfWork, INotificationDispatcher eventHandler)
: base(unitOfWork, eventHandler)
{
}
async Task IRepository.CreateAsync(Aggregate aggregate)
{
await base.AddAsync(aggregate);
}
}
What is it that I'm doing wrong or missing ?

We normally do not have to mock a method of an interface which doesn't return any unless I'm missing something in your question.
public class CreateUseCaseTests
{
[Fact]
public async Task HandleAsync_ShouldCreateRequest()
{
// Arrange
var repositoryMock = new Mock<IRepository>();
var sut = new CreateUseCase(repositoryMock.Object);
// Act
await sut.HandleAsync(new CreateRequest());
// Assert
repositoryMock.Verify(x => x.CreateAsync(It.IsAny<Aggregate>()), Times.Once);
}
}

I don't think your problem is with the Moq setup at all. The problem is that the unit test runs the meaningful code using Task.Run(), which spawns off a new thread. Then back on the original thread, you immediately test whether the Moq setup has been fulfilled. Since the code under test is launched on a different thread, there is a very real chance that the test for success comes before the code under test is executed.
You should change your unit test to run the test method using async & await, rather than spinning off a new thread. Note that the signature of the test case changes from void to async Task, and we await the code we're testing.
public class Test
{
[Fact]
public async Task Test_Create()
{
var repositoryMock = new Mock<IRepository>();
repositoryMock
.Setup(repo => repo.CreateAsync(It.IsAny<Aggregate >()))
.Returns(Task.CompletedTask);
var useCase = new CreateUseCase(repositoryMock.Object);
await useCase.HandleAsync(new CreateRequest());
repositoryMock.VerifyAll();
}
}

C# mocking generic repository using Moq

I have implemented generic repository in my project. Now I am writing test cases for my consumer. I am trying to mock database function through Moq but I am getting values from database rather than the one I faked through Moq. Below I am sharing my implementation. Hoping someone will help me in pointing out the mistake I made.
My interface:
public interface IEventsRepository<T> : IRepository<T> {
T GetEventsByEventId(int eventId); }
My class:
public class EventsTableRepository : EFDBRepository<EventsModel>, IEventsRepository<EventsModel> {
public EventsModel GetEventsByEventId(int eventId)
{
return _dbSet.Where(x => x.EventID == eventId).FirstOrDefault();
}
}
My Consumer:
public static Response<string> EventsAccept(EventsAlertsRequest logMsgId)
{
IEventsRepository<EventsModel> eventsRepo = (IEventsRepository<EventsModel>)RepositoryLocator.GetRepositoryObject(STMEnums.RepositoryName.EventsTableRepository.ToString());
EventsModel eventmodel = new EventsModel();
eventmodel = eventsRepo.GetEventsByEventId(eachlogMsgId);
return EventStatusChangeResponse;
}
Test Method:
public void EventsAcceptSuccessTest()
{
EventsModel eventmodel = new EventsModel();
eventmodel.Message = "TEST";
Mock<IEventsRepository<EventsModel>> obj = new Mock<IEventsRepository<EventsModel>>();
obj.Setup(m => m.GetEventsByEventId(Moq.It.IsAny<int>())).Returns(eventmodel);
EventStatusChangeResponse = Diagnostics_.EventsAccept(logMsgId);
Assert.AreEqual(eventmodel.Status, EventStatus.ACCEPTED);
}

No where in the provided example is the mock being injected into the subject under test. Also it looks like the subject method under test is using static Service Locator anti-pattern to get the desired model. Making an assumption here as the rest of the class is not shown in relation to that variable.
The locator would need to have been an injected abstraction to allow an opportunity to mock its expected behavior
public class Consumer {
private IRepositoryLocator RepositoryLocator;
public Consumer(IRepositoryLocator RepositoryLocator) {
this.RepositoryLocator = RepositoryLocator;
}
public Response<string> EventsAccept(EventsAlertsRequest logMsgId) {
IEventsRepository<EventsModel> eventsRepo = (IEventsRepository<EventsModel>)RepositoryLocator.GetRepositoryObject(STMEnums.RepositoryName.EventsTableRepository.ToString());
EventsModel eventmodel = new EventsModel();
eventmodel = eventsRepo.GetEventsByEventId(eachlogMsgId);
return EventStatusChangeResponse;
}
}
This would then mean that the locator would also have to be mocked properly for the test to be exercised to completion.
public void EventsAcceptSuccessTest() {
//Arrange
var eventmodel = new EventsModel() {
Message = "TEST"
};
var repositoryMock = new Mock<IEventsRepository<EventsModel>>();
repositoryMock
.Setup(_ => _.GetEventsByEventId(It.IsAny<int>()))
.Callback((int id) => {
eventmodel.EventID = id;
eventmodel.Status = EventStatus.ACCEPTED;
})
.Returns(eventmodel);
var locatorMock = new Mock<IRepositoryLocator>();
locatorMock.Setup(_ => _.GetRepositoryObject(It.IsAny<string>())).Returns(repositoryMock.Object);
var subject = new Consumer(locatorMock.Object);
//Act
var response = subject.EventsAccept(logMsgId);
//Assert
Assert.AreEqual(eventmodel.Status, EventStatus.ACCEPTED);
}

Moq WebApi async method

I'm new to testing with Moq, so I'm confused a bit regarding ReturnsAsync.
Here is my test method, where I'm expecting ReturnsAsync should receive type that will be returned by method defined in Setup. Am I right?
But seemed ReturnsAsync should have the other signature - it's looking for Func delegate.
[TestClass]
public class TourObjectControllerTest
{
[TestMethod]
public async Task GetTourObjects()
{
var mockService = new Mock<ITourObjectService>(MockBehavior.Default);
mockService.Setup(x => x.GetAll()).ReturnsAsync(new Task<IEnumerable<TourObjectDTO>>);
var controller = new TourObjectController(mockService.Object);
var result = await controller.Get();
Assert.IsNotNull(result);
Assert.AreSame(typeof(TourObjectViewModel), result);
}
}
Method under test:
public async Task<IEnumerable<TourObjectViewModel>> Get()
{
IEnumerable<TourObjectViewModel> viewmodel = null;
try
{
var tourobjects = await _tos.GetAll();
viewmodel = Mapper.Map<IEnumerable<TourObjectViewModel>>(tourobjects);
}
catch (Exception ex)
{
Log.ErrorFormat("Method:{0} <br/> Error: {1}", System.Reflection.MethodBase.GetCurrentMethod().Name, ex);
}
return viewmodel;
}

Pass an actual result.
Assuming ITourObjectService.GetAll() returns Task<IEnumerable<TourObjectDTO>>
eg
[TestClass]
public class TourObjectControllerTest
{
[TestMethod]
public async Task GetTourObjects()
{
var fakeData = new List<TourObjectDTO>() {
new TourObjectDTO { ... }
};
var mockService = new Mock<ITourObjectService>(MockBehavior.Default);
mockService.Setup(x => x.GetAll()).ReturnsAsync(fakeData);
var controller = new TourObjectController(mockService.Object);
var result = await controller.Get();
Assert.IsNotNull(result);
Assert.IsTry(typeof(IEnumerable<TourObjectViewModel>).IsAssignableFrom(result.GetType());
}
}

ReturnsAsync() should take a return value as the paramter instead of Task<TReurnValue>. For example, next 2 lines of code are equal (by behavior):
mockService.Setup(x => x.GetAll()).ReturnsAsync(new List<TourObjectDTO>());
mockService.Setup(x => x.GetAll()).Returns(Task.FromResult(new List<TourObjectDTO>()));
You need to replace new List<TourObjectDTO>() with your test data which you want to retrieve in the test from the mock. For example, you can create just few test values:
var testData = new [] { new TourObjectDTO(1, "test1"), new TourObjectDTO(2, "test2") };
mockService.Setup(x => x.GetAll()).ReturnsAsync(testData);
or create fake data generator if needed.
Note that ReturnsAsync() is only available for methods that return a Task<T>. For methods that return only a Task, .Returns(Task.FromResult(default(object))) can be used.