Flutter Unit Testing That Actually Catches Bugs

Core Principle

Tests must verify REAL behavior, not mock behavior. If your test can't catch a real bug, delete it—it gives false confidence.

The 5 Laws of Bug-Catching Unit Tests

1. Test BEHAVIOR, not implementation
2. Test BOUNDARIES, not just happy path
3. Test ERROR paths explicitly
4. Mock at the LOWEST possible level
5. Every test must have a REASON — "what bug does this catch?"

Flutter/Dart Testing Patterns