test-driven-development

Test-driven development eliminates regressions by enforcing a RED/Green/Refactor cycle: you write a failing test for new behavior, implement the smallest code change to make it pass, and then safely refactor without altering the proven behavior.

Yes, test-driven development supports browser runtime verification by pairing tests with OpenCode browser tools, and optionally Playwright MCP or DevTools MCP, to validate changes that affect the browser across integration boundaries.

The best way to avoid flakiness is using a sensible test pyramid with mostly small unit tests, preferring outcome-based assertions over interaction-based assertions, and avoiding testing framework internals to ensure reproducible verification.

Yes, test-driven development works for modifying existing functionality by writing a failing test that defines the desired new behavior, then implementing the minimal logic change until the test passes with deterministic assertions.

The RED/Green/Refactor cycle prevents regressions and uncertainty by requiring you to prove behavior with failing tests first, ensuring your subsequent code changes satisfy requirements for reproducible verification via an evidence-focused approach.