Fake generic method with FakeItEasy without specifying type

Question

I wonder if there is anyway one can fake up a generic method call, for all possible types (or specified sub-types)?

For example, suppose we have this wonderful IBar interface.

public interface IBar
{
    int Foo<T>();    
}

Can I fake a dependency to this IBar's Foo call, without having to specify T being any specific type?

[TestFixture]
public class BarTests
{
    [Test]
    public void BarFooDoesStuff()
    {
        var expected = 9999999;
        var fakeBar = A.Fake<IBar>();

        A.CallTo(() => fakeBar.Foo<T>()).Returns(expected);

        var response = fakeBar.Foo<bool>();

        Assert.AreEqual(expected, response);
    }
}

Thanks!

Answer 1

I'm not aware of any way to do this directly. I don't think DynamicProxy (which FakeItEasy uses) supports open generic types. However, there's a workaround, if you're interested.

There's a way to specify a call to any method or property on a fake. Check out the Where and WithReturnType bits in this passing test:

[TestFixture]
public class BarTests
{
    [Test]
    public void BarFooDoesStuff()
    {
        var expected = 9999999;
        var fakeBar = A.Fake<IBar>();

        A.CallTo(fakeBar)
            .Where(call => call.Method.Name == "Foo")
            .WithReturnType<int>()
            .Returns(expected);

        var response = fakeBar.Foo<bool>();

        Assert.AreEqual(expected, response);
    }
}

Still, though, I'm curious about the use for this. Do you have an example test that actually uses the faked interface as a dependency?