Thanks for following up on this: I was really surprised by how much air this paeon to, idk, TDD, took out of the comments by getting off-topic.

Before you commented, I started poking at what you described for 15 minutes, then forget about it and fell asleep. Now I remembered, and I know it's viable and IIUC it's almost certainly going to make a big difference in my work practice moving forward. Cheers.