How to test your code effectively: a practical testing tutorial
Unit, integration, and end-to-end (E2E) testing form a pyramid of verification: fast, cheap unit tests guard business logic; slower, more integration-focused tests verify interactions between components; and a smaller set of fragile but user-visible E2E tests ensure real-world flows work.
Unit tests: what to test and how
Focus on pure logic and edge cases. Test a function’s input-output behavior with representative inputs, including boundary and error conditions.
Isolate units: test them independently from dependencies via mocks or stubs. This keeps tests fast and deterministic.
