Testing verifies software meets expectations and reveals hidden defects. You write unit tests, integration tests, and system tests. Computer science studies logic correctness, but software engineering leverages test automation for scale and time. Treat tests as core code in languages like TypeScript or Python.
Unit Tests: Validate individual functions isolated from other code. They execute in milliseconds.
Integration Tests: Ensure modules cooperate as designed. They connect separate moving parts.
End-to-End Tests: Simulate user behavior via automated browsers. They traverse the whole stack.
Test-Driven Development: Write tests before writing logic. The process forces thoughtful interface design.
Behavior-Driven Development: Map business requirements into executable scenarios.
Tests reduce defects. Code coverage tools measure tested logic paths. Quality assurance professionals demand comprehensive coverage.