Ninety seconds, and what changed about how people work

A suite at four minutes forty that people ran on push, and at ninety seconds that people run on save.

the observable change, over a month:

  local runs per developer per day   4 → 22
  pushes with a failing test         11% → 3%
  time from writing a bug to seeing
    it fail                          ~14 min → ~40 sec

and the one that surprised me:
  commits per day went UP, because a green suite is
  the thing people commit against and they were
  waiting for it.

There is a threshold below which running the suite stops being a decision, and it is somewhere under two minutes — above it people batch, below it they do not. The commit rate change is the second-order effect and is the one that suggests the four-minute suite had been shaping the work rather than merely verifying it.