No programmer is perfect. No guarantee is made that bugs do not exist in the code that is provided. However, most of the code has been tested extensively; so, check your code as well as any code that is supplied. Reporting and, perhaps, correcting bugs in supplied code is just one way to improve the quality of the course and earn brownie points with Meesh. Of course, we have no plan to support validation of outputs except via correctness as tested on the submit server.