C# – Using Moq to Mock a Func<> constructor parameter and Verify it was called twice

cfunctional-testingmoqunit testing

Taken the question from this article (How to moq a Func) and adapted it as the answer is not correct.

public class FooBar
{
    private Func<IFooBarProxy> __fooBarProxyFactory;

    public FooBar(Func<IFooBarProxy> fooBarProxyFactory)
    {
        _fooBarProxyFactory = fooBarProxyFactory;
    }

    public void Process() 
    {
        _fooBarProxyFactory();
        _fooBarProxyFactory();
    }
}

I have a need to mock a Func<> that is passed as a constructor parameter, the assert that the func was call twice.

When trying to mock the function var funcMock = new Mock<Func<IFooBarProxy>>(); Moq raises and exception as the Func type is not mockable.

The issue is that without mocking the func it is not possible to verify that the func was called (n) times. funcMock.Verify( (), Times.AtLeast(2));

Best Answer

I don't think it is necessary to use a mock for the Func.

You can simply create an ordinary Func yourself that returns a mock of IFooBarProxy:

int numberOfCalls = 0;
Func<IFooBarProxy> func = () => { ++numberOfCalls;
                                  return new Mock<IFooBarProxy>(); };

var sut = new FooBar(func);

sut.Process();

Assert.Equal(2, numberOfCalls);

Related Solutions

C# – How to verify that method was NOT called in Moq

Run a verify after the test which has a Times.Never enum set. e.g.

_mock.Object.DoSomething()
_mock.Verify(service => service.ShouldntBeCalled(), Times.Never);

How to Verify another method in the class was called using Moq

You are having this problem because you are mocking what you are testing. This doesn't make sense.

You are correct that Moq will replace the implementation of your method with its own. The reason is you are supposed to use Moq to mock things the class you are testing calls, not the class you are testing itself.

This test would be appropriate if your code were designed thusly:

public class ClassA
{
    BusinessLogicClass bl;
    public ClassA(BusinessLogicClass bl)
    {
         this.bl = bl;
    }

    public void Save()
    {
        bl.ShouldBeCalled();
    }
}

public class BusinessLogicClass
{
    public virtual void ShouldBeCalled()
    {
        //This should get executed
    }
}

And here is the correct test of that method now:

[TestFixture]
public class ClassA_Test
{
    [Test]
    public void Save_ShouldCallShouldBeCalled()
    {
        //Arrange
        var mockBLClass = new Mock<BusinessLogicClass>();
        mockBLClass.Setup(x => x.ShouldBeCalled()).Verifyable();

        //Act    
        ClassA classA = new ClassA(mockBLClass.Object);
        classA.Save();

        //Assert
        mockBLClass.VerifyAll();
    }
}

The key lesson here is that you mock/stub what your test needs to run, not what you are testing itself.

Hope this helps, Anderson

Best Answer

Related Solutions

C# – How to verify that method was NOT called in Moq

How to Verify another method in the class was called using Moq

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