discover-testing

Unit testing validates individual functions by writing test cases that check expected outputs. Start by choosing a framework like pytest or unittest, write tests alongside your code, and run them frequently to catch bugs early before integration.

Unit tests verify isolated functions; integration tests check how components work together; E2E tests validate entire workflows from user input to output. Each catches different failure types—use all three for comprehensive coverage.

Test coverage tracks what percentage of code your tests execute. Tools like coverage.py generate reports showing untested lines. Aim for 80%+ coverage, but prioritize testing critical paths over hitting arbitrary targets.

TDD focuses on correctness; performance testing validates speed and resource use. Write unit and integration tests first with TDD, then add performance tests to ensure your code meets latency and throughput requirements.

Apply TDD by writing failing tests first, then implement code to pass them. Add integration tests once components connect, then E2E tests for full workflows. Use test coverage metrics to identify gaps across all testing layers.