Every animated figure in the places is driven by the same small set of clips, and each clip carries a number saying how fast the body is travelling in it. Match that to the speed the character is actually moving and the feet plant. Get it wrong and they skate.

The numbers were guesses. Reasonable ones, typed in once and then inherited by everything downstream as if they had been measured. When I finally measured them off the clips, the walk was close and the run was out by about 65%. That is not a subtle error, and the reason nobody caught it is that a skating foot reads as "animation is hard" rather than as a wrong constant.

Measuring them also exposed a gap: there was a walk and there was a run, and nothing in between, so anything moving at a jog had to pick a clip and lie about it. There is a jog now. A test holds all three numbers against the clips themselves, so the next one cannot quietly reintroduce the drift.

The sweep that came out of this found nine defects in total, including statues playing an idle loop and crowds walking in perfect lockstep because every one of them started on frame zero. All of it is on a branch. Writing a test that measures the asset rather than trusting a number typed beside it is the part worth keeping.