Hour 0: "I'm gonna finish implementing a feature today." Hour 1: "Why isn't this working?? This is supposed to work!" Hour 2: Google, SO, RailsForum, Github, GoogleGroup and even, IRC Hour 5: "I have tried literally everything. I feel stupid" "..." "I might as well try restarting my computer too." Hour 5: When the restart didn't work "Yes, I am stupid." Hour 6: "Great! I'm stuck at a scenario and a half let alone implementing a feature." Hour 8: When I eventually found the bug. "WHY AM I SO STUPID! What was I thinking!?"
Moral of the story:
Just because it’s simply one line of code, do not implement unrelated feature B (and forget about it), when you are working on feature A. Especially during TDD.