I've been writing a small utility to help us do some configuration setup for testing. It needs to walk a directory structure, find all instances of a specific xml file, and then make some modifications to the file.

I TDD'd the class that does the XML file stuff, and I'm confident that it's working well. I'm now going to do the class to walk of the directory structure and find the files.

And there is my dilemna. I don't know if I'm going to do TDD on that.

I know exactly how to write it, I've written it before, and my experience is that that is code that never changes nor breaks. And, figuring out how to write tests for it is going to be somewhat complex because I'll have to isolate out the live file system parts.

So, I've already decided what I'm going to do, but I'm curious what you think. Does YAGNI apply to test code, or is that the first step to the dark side?