Using a AutoFixture created mock in a concrete implementation

Question

I have the following issue with regards to AutoFixture, explained in code

public SUT(IConcrete concrete)
{
    DTO BuildDTO()
    {
         return new DTO 
         {
             URL = concrete.GetString(arg1, arg2);
         };
    }
}

public Concrete : IConcrete
{
    public Concrete(ISomeHandler someHandler)
    {
        ...
    }

    public GetString(obj arg1, obj arg2)
    {
        return someHandler.GetUri(arg1, arg2);
    }
}

public void Test(
[Frozen] Mock<ISomeHandler> someHandler,
SUT mySUT)
{
    someHandler.Setup(...);
    mySUT.DoStuff();
    //assert everything went as expected
}

My problem is simply, how do I register the IConcrete with AutoFixture, in such a way that I can access the frozen mock that should be injected into it in the test case?

In actuality, this is about injecting a HttpRequestMessage into a URL Resolver, which is used in a Handler, called from the controller in a Web API project.

I have tried to register the IConcrete with an autofixture created mock

fixture.Register<IConcrete>(new Mock<ISomeHandler>());

but then I cannot access this mock in the unit test and setup the return value.

Thanks in advance for any and all help :)

If `SUT` depends on `IConcrete`, then why even care about `ISomeHandler`? — Mark Seemann, Jul 14 '16 at 19:22
I care about the ISomeHandler because it is outputting an url and I would like to verify this is generated correctly. — Jesper Bangsholt, Jul 15 '16 at 05:42
In the code provided, there's no interaction between `SUT` and `ISomeHandler`. — Mark Seemann, Jul 15 '16 at 07:11
I have added in more code to show the interactions between the `SUT` and `ISomeHandler`. — Jesper Bangsholt, Jul 15 '16 at 07:22
So the issue boils down to: How to get AutoFixture to register the IConcrete with a mocked ISomeHandler. — Jesper Bangsholt, Jul 15 '16 at 07:23
`SUT` still doesn't interact with `ISomeHandler`. It calls `IConcrete.GetString`. You only need to provide a Test Double for `IConcrete`. — Mark Seemann, Jul 15 '16 at 07:58
Thank you Mark - I realized I need to test the IConcrete for it self and then in this case with the SUT I can use the autofixture generated URLs, as I know that the IConcrete in itself will generate the correct URLs. — Jesper Bangsholt, Jul 15 '16 at 08:37

score 3 · Accepted Answer · edited May 23 '17 at 11:51

In order to allow AutoFixture generating mocks the AutoMocking Container needs to be enabled.

You need to do the following:

Create the AutoMoqAttribute:

public class AutoMoqDataAttribute : AutoDataAttribute
{
  public AutoMoqDataAttribute()
    : base(new Fixture().Customize(new AutoMoqCustomization()))
  {
  }
}

Decorate your test with the new attribute:

[Theory, AutoMoqData]
public void Test(
  [Frozen] Mock<ISomeHandler> someHandler,
  Sut sut)
{
  someHandler.Setup(s => s.DoStuff()).Returns("123");
  Assert.Equal("123", sut.SomeHandler.DoStuff());
}

Where Sut and ISomeHandler are the following:

public class Sut
{
  public Sut(ISomeHandler someHandler)
  {
    SomeHandler = someHandler;
  }

  public ISomeHandler SomeHandler { get; }
}

public interface ISomeHandler
{
  string DoStuff();
}

Using a AutoFixture created mock in a concrete implementation

1 Answers1