Mocking a protected generic method with Moq

Question

To mock a protected virtual (non-generic) method in Moq is easy:

public class MyClass
{
....
      protected virtual int MyMethod(Data data){..}
}

And to mock it:

myMock.Protected().Setup<int>("MyMethod", ItExpr.Is<Data>( ...

I could not find a way to use the same technique if the protected method is generic, like:

protected virtual int MyMethod<T>(T data)

Any idea how to do it, besides using a wrapper class to override that method, is highly appreciated.

I'm not sure if you can. The first thing I tried was passing MyMethod`1[T] to Setup(), but that didn't seem to fool it. You might try playing with that, anyway. — Erik Dietrich, Feb 23 '12 at 16:51

score 7 · Accepted Answer · edited May 23 '17 at 12:09

I've checked the source and it seems mocking protected generic methods with Moq is not supported:

The Protected() method creates an instance of a class ProtectedMock<T> which uses the following method to get the method that you want to mock:

private static MethodInfo GetMethod(string methodName, params object[] args)
{
    return typeof(T).GetMethod(
           methodName,
           BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public,
           null,
           ToArgTypes(args),
           null);
}

It uses Type.GetMethod to get the method for mocking, but GetMethod (although MSDN states differently) don't play nice with generics, see:

GetMethod for generic method

Get a generic method without using GetMethods

Side note: In my opinion mocking a protected member is a code smell, and I would rather try to avoid it anyway with refactoring my design (beside that it's not supported in Moq).

I totally agree with the code smell. But sometimes in a more complex scenario this can easy the testing. I.e. if you have very "similar" functionality for a bunch of methods, and you really just want to verify the the publicly exposed parts do map properly the parameters to pass them down. — Sunny Milenov, Feb 27 '12 at 17:06

score 6 · Answer 2 · answered Dec 10 '19 at 15:46

It can be done since Moq 4.13 (2019-09-01) by using As for protected methods and It.IsAnyType for generic type arguments:

classUnderTest.Protected().As<IMyMethodMock>().Setup(x => x.MyMethod(It.IsAny<It.IsAnyType>())).Returns(...);

And create the following interface for the mocking method:

public interface IMyMethodMock
{
    int MyMethod<T>(T data);
}

Full example:

[TestClass]
public class MockingProtectedGenericFixture
{
    [TestMethod]
    public void test()
    {
        // Arrange
        var classUnderTest = new Mock<MyClass>();
        classUnderTest.Protected().As<IMyMethodMock>().Setup(x => x.MyMethod(It.IsAny<It.IsAnyType>())).Returns(2);

        // Act
        var resForStringData = classUnderTest.Object.GetNumber("DataString");
        var resForBooleanData = classUnderTest.Object.GetNumber(true);

        // Assert
        Assert.AreEqual(2, resForStringData);
        Assert.AreEqual(2, resForBooleanData);
    }
}

public class MyClass
{
    public int GetNumber<T>(T data)
    {
        return MyMethod(data);
    }

    protected virtual int MyMethod<T>(T data)
    {
        return 1;
    }
}

public interface IMyMethodMock
{
    int MyMethod<T>(T data);
}

fantastic! worked like a charm! – samar Dec 14 '21 at 14:03 — samar, Dec 14 '21 at 14:03

Mocking a protected generic method with Moq

2 Answers2