How to mock a generic method with delegate in it using Fakes

Question

I am having a method as below which I want to mock using Fakes. Any help in this regard is really appreciated?

IEnumerable<T> ExecuteReader<T>(
    string commandText, 
    Func<IDataRecord, T> returnFunc, 
    int timeOut = 30);

Answer 1

Assuming you've generated the fakes assembly for the interface/class in question then it depends if you're using an interface (or virtual method) to define the method or only a class. If an interface or virtual method, you can use a stub like

    [TestMethod]
    public void StubFuncTest()
    {
        StubITestReader stubClass = new StubITestReader();
        stubClass.ExecuteReaderOf1StringFuncOfIDataRecordM0Int32<int>((str, func, timeout) =>
        {
            int[] retVal = {12, 25, 15};
            return retVal;
        });

        ITestReader reader = stubClass;
        IEnumerable<int> curInt = reader.ExecuteReader<int>("testText", TestFunc);
        foreach (var i in curInt)
        {
            Console.WriteLine(i);
        }
    }

or if just a standard method, you'll need to use a shim (I would advise to use the first option)

    [TestMethod]
    public void ShimFuncTest()
    {
        TestUnitTestClass tutClass = new TestUnitTestClass();
        using (ShimsContext.Create())
        {
            ShimTestUnitTestClass shimClass = new ShimTestUnitTestClass(tutClass);
            shimClass.ExecuteReaderOf1StringFuncOfIDataRecordM0Int32<int>((str, func, timeout) =>
            {
                int[] retVal = {12, 25, 15};
                return retVal;
            });

            IEnumerable<int> curInt = tutClass.ExecuteReader<int>("testText", TestFunc);
            foreach (var i in curInt)
            {
                Console.WriteLine(i);                    
            }
        }
    }

Adding response to comment
It's a bit easier for normal methods. Using the stub, it would be something like

    [TestMethod]
    public void StubRegFuncTest()
    {
        StubITestReader stubClass = new StubITestReader();
        stubClass.ExecuteNonQueryStringInt32 = (str, timeout) => timeout * 2;

        ITestReader reader = stubClass;
        int curInt = reader.ExecuteNonQuery("testText");
        Console.WriteLine(curInt);
        curInt = reader.ExecuteNonQuery("testText", 10);
        Console.WriteLine(curInt);
    }

The not-so-obvious difference is the generic method is enclosed in parenthesis while the normal method is just lambda expression and code block.