Mocking Generic Methods With NMock2
Recently I was asked how to mock a generic method, now that NMock2 supports generics. Here's how:
Suppose you have this interface:
public interface IMyInterface
{ T DoStuff<T>();
}
And this class using IMyInterface:
public class MyClass
{ private IMyInterface mi_;
public MyClass(IMyInterface mi)
{ this.mi_ = mi;
}
public string DoSomething()
{ return this.mi_.DoStuff<string>();
}
}
Now, you want to write a unit test where you validate that if DoStuff<string> returns Ploeh, MyClass.DoSomething will also return Ploeh. On the version of NMock2 currently installed on my laptop, this is easily done like this:
[TestMethod]
public void ValidateDoSomething()
{ Mockery mocks = new Mockery();
IMyInterface mi = mocks.NewMock<IMyInterface>();
Expect.Once.On(mi).Method("DoStuff").Will(Return.Value("Ploeh"));
MyClass mc = new MyClass(mi);
string result = mc.DoSomething();
Assert.AreEqual<string>("Ploeh", result); mocks.VerifyAllExpectationsHaveBeenMet();
}
The only thing which is slightly surprising here is that the method name expected is DoStuff, without any indications of generics - I first expected that I should have indicated the method name as DoStuff`1, but apparently, NMock2 doesn't care whether you are expecting a generic or non-generic version of a method (if DoStuff had had a non-generic overload).
Note that this is based on a release candidate of NMock2, so there's no guarantee that this will work exactly identical in the final release.
