I provided some sample code recently, it was experimental, rolled-at-home 'research' code that was, I think, in line with the mission of the team I had applied to, complete with test data and instructions. Needless to say, the interviewer didn't want to talk about what the code did but instead grilled me on various technical language details. In some ways it is a great litmus test, because the people I have enjoyed working with in the past would have had endless questions for me about what the code was actually doing...