A few years back I saw something similar where subreddits were presented like a tree, based on topics (and popularity, I think). Made it easy to drill down to interesting niche subreddits.
You are skipping a step there - it's red -> green -> refactor
As for "tactical programming instead of strategic design" - that's entirely up to the developer and how they approach the problem. if you are prone to neglecting the design you'll do it any way. If anything, (actually) practicing TDD would force you to come up with better design.
All other Python options I've seen feel too involved or leak too much into your code. Lagom seems to balance everything just right.
Thank you!