Mock AutoMapper Mapper.Map call using Moq

Question

Whats the best way to setup a mock expection for the Map function in AutoMapper.

I extract the IMapper interface so I can setup expects for that interface. My mapper has dependencies, so I have to pass those in to the mapper.

What happens when I create 2 instances of my mapper class, with 2 different dependency implementations? I asume that both mappers will use the same dependency instance, since the AutoMapper map is static. Or AutoMapper might even throw an exception because I try to setup 2 different maps with the same objects.?

Whats the best way to solve this?

public interface IMapper {
    TTarget Map<TSource, TTarget>(TSource source);
    void ValidateMappingConfiguration();
}

public class MyMapper : IMapper {
    private readonly IMyService service;

    public MyMapper(IMyService service) {
        this.service = service
        Mapper.CreateMap<MyModelClass, MyDTO>()
            .ForMember(d => d.RelatedData, o => o.MapFrom(s =>
                service.getData(s.id).RelatedData))
    }

    public void ValidateMappingConfiguration() {
        Mapper.AssertConfigurationIsValid();
    }

    public TTarget Map<TSource, TTarget>(TSource source) {
        return Mapper.Map<TSource, TTarget>(source);
    }
}

Answer 1

Whats the best way to setup a mock expection for the Map function in AutoMapper[?]

Here's one way:

var mapperMock = new Mock<IMapper>();
mapperMock.Setup(m => m.Map<Foo, Bar>(It.IsAny<Foo>())).Returns(new Bar());

Answer 2

http://richarddingwall.name/2009/05/07/mocking-out-automapper-with-dependency-injection/

Points out another way of handling dependencies to AutoMapper, which basically will replace my attempt to extract my own IMapper interface. Instead I will attempt to use the existing IMappingEngine as dependency for my classes, to see if that works.

Answer 3

What you need to do is setup AutoMapper like this (StructureMap is IoC). Then you can make your services dependent on IMappingEngine. From there mocking it should be very easy.

public class AutoMapperConfigurationRegistry : Registry
    {
        public AutoMapperConfigurationRegistry()
        {
            ForRequestedType<Configuration>()
                .CacheBy(InstanceScope.Singleton)
                .TheDefault.Is.OfConcreteType<Configuration>()
                .CtorDependency<IEnumerable<IObjectMapper>>().Is(expr => expr.ConstructedBy(MapperRegistry.AllMappers));

            ForRequestedType<ITypeMapFactory>().TheDefaultIsConcreteType<TypeMapFactory>();

            ForRequestedType<IConfigurationProvider>()
                .TheDefault.Is.ConstructedBy(ctx => ctx.GetInstance<Configuration>());

            ForRequestedType<IConfiguration>()
                .TheDefault.Is.ConstructedBy(ctx => ctx.GetInstance<Configuration>());
        }
    }