Well, the spies have it.
You'll see in the responses to the last Verg-o-nomics entry that I'd screwed up the implementation of the spies, and that's what's caused all the pain.
Stubbing your foot on the inheritance tree
It stands to reason that you should use 100% configurable spies/stubs so that they return 100% predictable results for the indirect inputs to your SUT ... you can even set the stubs to fail on purpose and exercise a different facet of your SUT.
If, on the other hand, you're just lazy (like I was) and directly subclass the real components or "DOCs" to create your spy/stub classes, you may have to roll real test data, or your tests may crash!
Tests have been much smoother so far... though I've been mostly refactoring to remove key components from classes who were delegating to too many delegatees... and consolidating them by overall responsibility into larger delegatees.
You can take a peek at the actual refactoring on the Death Star whiteboard... it's the PixelConverter template being extracted from the PixelDepthToScreen template... which will be renamed 'BitdepthToScreen'.
Overall, TDD has been a calming influence and steadying force throughout... because refactoring is painless, and I know right away if I've broken something when the tests squeal.
It shouldn't be too long before this is done.
I'm going to experiment with putting up a step-by-step TDD session (warts and all) soon... as soon as I can figure out how to record the session (S-Video out to VCR?) and then translate it.
Who knew "Tile Loading" would be the major component, in contrast to "Tile Rendering", or even "Tile Map Scrolling"?