// Create default mocks, and return values for the function position.
        void MockFunctionPosition(string functionName)
        {
            var    mockFunctionPosition = Substitute.For <IDebugFunctionPosition2>();
            string value;

            mockFunctionPosition.GetFunctionName(out value).Returns(x =>
            {
                if (functionName != null)
                {
                    x[0] = functionName;
                    return(0);
                }
                return(1);
            });
            mockMarshal.GetFunctionPositionFromIntPtr(Arg.Any <IntPtr>()).Returns(
                mockFunctionPosition);
        }