Product · Simulator
Differ uses your app the way real people would and surfaces what breaks and what makes them quit.
Differ works from a copy of your repo. Your source is never touched.
A test script clicks exactly where you told it to. A real user doesn't. Differ runs your app through a cast of personas. Each one moves through your app the way that kind of person would.
Test scripts only cover the paths you thought to write. The simulator finds the ones you didn't. The errors that only show up once someone actually uses the app, because no one had clicked through it that way yet.
To your app, a simulated session is the real thing. Nothing is mocked or stubbed, so your app responds exactly as it would to a person. What the simulator finds is what your users would have.