Test

Pick the Right Layer First

Writing tests at the wrong layer is the most common testing mistake. A unit test that mocks everything doesn't catch integration bugs; an E2E test for a pure function is slow and fragile.

Layer	What it tests	Speed	When to use
Unit	Pure functions, isolated logic	~ms	Business logic, utilities, transformations
Integration	Service boundaries, DB queries, API contracts	~seconds	Repository layer, HTTP handlers, queue consumers
E2E	User flows in a real browser	~minutes	Critical paths only (checkout, auth, onboarding)

The pyramid holds: many units, fewer integrations, minimal E2E.

Detect the Framework

Check before choosing: