1. Testing provides valuable feedback that breaks illusions about code quality and helps improve software. Testing focuses on both checking code systematically and exploring it openly.
2. The context of testing matters - testing in production has different risks than testing in development. Skilled testers explore products and businesses rather than just checking facts.
3. Testers help dispel illusions about code by finding bugs, not just defects, and empirical evidence is more useful than speculation alone. The role of testing is changing as development processes become more automated.