I got bitten today by a severe lack of testcases biting off my ankles. Could 've used that. I'm converting a couple of thousand pages from plain html (plus lots of PDFs and images) to plone (and custom) documents.

While I was testing lots of intermediary steps, I completely forgot to test whether in the end the documents were ending up in the right spot. Ouch.

Doing that from the beginning would have made the whole process much more manageable. Ah well, one lives to learn :-)