Javascript Testing

Use this SKILL when setting up or validating test infrastructure for JavaScript/TypeScript projects, diagnosing flaky async tests, or designing reliable CI test suites.

Recommended runners:

• Jest (general-purpose, snapshot testing, good mocks)
• Vitest (Vite/Esm-native projects)
• Mocha + Chai + Sinon (explicit control)

Checklist

• AAA pattern (Arrange, Act, Assert) and descriptive test names
• Avoid shared mutable state across concurrent tests
• Proper async handling (return/await/promises)
• Reset mocks between tests

Templates & Examples

Example test file (Jest):

// __tests__/sum.test.js
const sum = require('../sum')

test('adds numbers', () => {
  expect(sum(1,2)).toBe(3)
})

Flaky-test triage CSV header:

File,TestName,ObservedBehavior,SuggestedFix tests/api.test.js,"handles slow response","timeout in CI","increase timeout; mock network; make deterministic"

Output requirements

• For each finding provide: file and line, risk, why it matters, minimal fix with code example.