tdd-workflow

Write failing tests first based on user journeys, then implement the minimal code to make them pass, and refactor while keeping tests green. This Skill structures that RED-GREEN-Refactor cycle with coverage verification at the end.

Check whether package.json scripts.test invokes jest/vitest or whether test files import from bun:test. Use bun test for Bun's native runner and bun run test only when the script delegates to Jest or Vitest, since mixing them is a common failure.

Unit tests cover individual functions and components in isolation, integration tests verify API endpoints and database or service interactions, and E2E tests use Playwright to automate complete user flows in a browser.

Use jest.mock with a factory that returns stubbed methods resolving canned data, such as a mocked supabase.from chain or a mocked searchMarketsByVector function. This isolates unit tests from external services.

Invoking Jest through npx or bun run in an ESM-only project can break, while bun test runs the suite natively. Detect the runner first via scripts.test, lockfiles, or the packageManager field before executing tests.

This Skill enforces a minimum of 80% across branches, functions, lines, and statements, configured via Jest coverageThresholds or bunfig.toml for Bun. Coverage reports identify untested edge cases and error paths.