Imagine this: While tackling a subtle bug in a complex application, you make a simple change that you think will address the issue. But when you run the tests, a whole bunch of seemingly unrelated tests start to fail. You reverse the change, and they pass again, so it’s most certainly your change causing the problem.
You reapply your fix, run the tests, and a distinct set of unrelated tests start to fail! You stare at the screen in bewilderment. You’re quite literally at a loss for words, reduced to gesturing futilely at the screen because none of this makes any sense at all.
Gesticulation Driven Development is when you don’t quite believe what’s happening on screen in front of you. Muted by frustration, the only way left to express yourself is by waving your hands.
Many developers never experience GDD, preferring instead the vigorous application of Profanity Driven Development.
Sometimes, however, what happens on screen is just so profoundly weird that words fail us.
Effectively responding to a situation involving GDD involves cutting yourself some slack - the computer is only doing what it’s told to do, so there must be a reasonable explanation for the unutterably weird thing you’re observing. A good place to start is by checking your assumptions.