Mocking Generic Method with NSubstitute
.net, c#, ncrunch, nsubstitute
Solution
NSubstitute doesn't support setting up multiple instances of a generic method automatically.
The way we'd normally see `IInstanceSource` used in a test is to configure it for a specific bit of code under test, so `T` would be known. If a single fixture needed to work for a few different `T`s, we could make configuration simpler by having a helper method like `ConfigureInstanceSource<T>()` which would do the configurations steps for a specific `T`.
In your case though it seems like you want a fixed behaviour for all fake instances of `IInstanceSource`, in which case I believe you are going the right way about it by hand-coding your own test double.
Problem
I have an interface with a number of generic methods. These methods perform operations based on the type of data that is passed in. How do I mock this with NSubstitute? At the moment, I had to resort to using a concrete class instead of a mock since I cannot handle all possible types that the method will be called with. ``` public interface IInstanceSource { bool CanCreate<T>(); T Create<T>(); void Register<T>(Func<T> creator); } public static IInstanceSource GetInstanceSource() { var _data = new Dictionary<Type, Func<object>>(); var a = Substitute.For<IInstanceSource>(); //code below fails since T is not defined. How do I make the code below accept any type? a.WhenForAnyArgs(x=>x.Register(Arg.Any<Func<T>>)).Do(x=> { /* todo */}); a.CanCreate<T>().Returns(x => _data[typeof (T)]); return a; } ``` thanks.