Swift performance

A cost is the work per run, times how often it runs. Build mode keeps costly work off hot paths while you write code. Diagnosis mode finds the work that got there, and its fix goes back through build mode.

Write your own fixtures, scenarios and counters for each app, since every app needs different ones.

Build mode

Run all steps for a new feature. For a review, run steps 4 to 6 on the diff.