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Reputation: 3746

IMapper mock returning null

I have an application in .net core in which I am using automapper in one of my service. Now the issue is I am writing test method and mocking automapper but it is returning null. Here is the service method:

var users = _mapper.Map<IList<User>>(data);

and here is mocking using Moq:

var userLogsList = new List<User>() { new User() {Id = "1234", Name= "Dummy User"}};
var mapperMock = new Mock<IMapper>();
mapperMock.Setup(m => m.Map<List<UserEntity>, IList<User>>(It.IsAny<List<UserEntity>>()))
.Returns(userLogsList);

Now this mock returining null everytime. What am i doing wrong?

Upvotes: 2

Views: 3980

Answers (3)

littleinstein
littleinstein

Reputation: 71

The reason you have to invoke automapper config is because, the UNIT Test cases instance runs outside of main application start up files/configs. Hence the auto mapper configuration has to be called and setup before any unit tests start to run. Ideally you place it in TestInitialize methods.

Upvotes: 1

Nkosi
Nkosi

Reputation: 247153

You can also consider using an actual IMapper instance configured specifically for the test.

// Arrange

//Configure mapping just for this test
var config = new MapperConfiguration(cfg => {
    cfg.CreateMap<User, UserEntity>();
    cfg.CreateMap<UserEntity, User>();
});

var mapper = config.CreateMapper(); // IMapper to be injected into subject under test

//...

If a dependency can be used without much knock on effect and minimal configuration then there is not always a reason to have to use a mock.

In this case the configuration is much simpler than creating a mock and you get the full functionality of the dependency with no additional work.

Upvotes: 8

Matt Dillard
Matt Dillard

Reputation: 14853

It looks like you've set up Moq to intercept calls to the IMapper.Map<TSource, TDestination>(TSource source) overload, but your code under test calls the IMapper.Map<TDestination>(object source) overload.

You should mock the latter:

var userLogsList = new List<User>() { new User() {Id = "1234", Name= "Dummy User"}};
var mapperMock = new Mock<IMapper>();
mapperMock.Setup(m => m.Map<IList<User>>(It.IsAny<object>()))
          .Returns(userLogsList);

I'm assuming the signatures for IMapper as described here.

Upvotes: 2

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