To be able to mock AutoMapper, we can use Dependency Injection to inject a mapper interface to the constructor of the calling code's class rather than using AutoMapper directly. Below is an example of such interface:
public interface IMappingService
{
TDest Map<TSrc, TDest>(TSrc source) where TDest : class;
}
Then create an implementation class for the interface. Note on line 5 that for this class we specify AutoMapper directly.
public class MappingService : IMappingService
{
public TDest Map<TSrc, TDest>(TSrc source) where TDest : class
{
return AutoMapper.Mapper.Map<TSrc, TDest>(source);
}
}
Next, bind the interface with the concrete class. Below is an example of how to do it with Ninject:
kernel.Bind<IMappingService>().To<MappingService>();
Then whenever we want to do mapping, we call the interface's Map method instead of using the AutoMapper's Mapper.Map() method.
public ViewResult List()
{
IEnumerable<Stuff> stuffs = stuffRepository.All;
List<StuffViewModel> model = mappingService.Map<IEnumerable<Stuff>, List<StuffViewModel>>(stuffs);
return View("List", model);
}
Please remember that mapping configurations need to be specified first before we could do any mapping. You can see this post to see how to set up the configurations.Now we can mock the mapper in our unit test. In the example below I use xUnit testing framework. As you can see; first we create a mock instance from the interface, setup what the Map method will return and then pass the mock object to the class constructor of the feature to be tested (line 6, 25 and 28).
[Fact]
public void ListPageReturnsStuffViewModels()
{
// Arrange
Mock<IStuffRepository> stuffRepository = new Mock<IStuffRepository>();
Mock<IMappingService> mappingService = new Mock<IMappingService>();
List<Stuff> stuffs = new List<Stuff>();
stuffRepository.Setup(r => r.All).Returns(stuffs.AsQueryable());
var viewModelStuffs = new List<StuffViewModel> {
new StuffViewModel { StuffID = 1/*,
Name= "Bip",
Description= "Colourful baby bip",
DateAdded = DateTime.Now,
UserID = 1 */
},
new StuffViewModel { StuffID = 2/*,
Name= "Socks",
Description= "Winter socks with animal figures",
DateAdded = DateTime.Now,
UserID = 1 */
}
};
mappingService.Setup(m => m.Map<IEnumerable<Stuff>, List<StuffViewModel>>(It.IsAny<IEnumerable<Stuff>>()))
.Returns(viewModelStuffs);
var controller = new StuffsController(stuffRepository.Object, mappingService.Object);
// Act
var result = controller.List() as ViewResult;
//var model = result.ViewData.Model as List<StuffViewModel>;
// Assert
var model = Assert.IsType<List<StuffViewModel>>(result.ViewData.Model);
Assert.Equal(2, model.Count);
}
