// 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); }