Co-Worker (who does not believe in unit tests): Okay. I just checked my changes in.

Me: There’s a bug in your code.

Co-Worker: How do you know? I just checked it in!

Me: It broke my unit tests. It looks like you’re not setting the flibbergibbet value correctly.

Co-Worker: What? How can you tell?

Me: JUnit showed me the difference.

Co-Worker: Oh. I guess I’ll fix it now. I would have found it eventually…

For what it’s worth, we’re handling Electronic Data Interchange documents – things that look like a page or so of line noise at a time. The bug was that one character wasn’t getting written to the output. My co-worker tests his code with the toString() and visual grep method. I’m not sure he would have ever caught the bug on his own. I keep trying to explain that unit tests are a Good Thing…