Jest

Full standards in jest.md. Always-on summary:

Structure:

• One describe( per module/class; one describe( per method inside
• Test names complete the sentence: it('returns null when user not found')
• Use expect( for all assertions — Arrange-Act-Assert with blank lines between sections

Setup / teardown:

• beforeEach( to reset state before each test; call jest.clearAllMocks( in beforeEach to prevent cross-test pollution

Mocking:

• jest.mock( calls go at the top of the file, before imports take effect
• Use mockReturnValue( or mockResolvedValue( to control return values
• Mock at the system boundary (HTTP, DB, filesystem) — not internal functions
• jest.spyOn() for partial mocks where you want the real implementation for some calls
• Always restore mocks: use jest.restoreAllMocks() in afterEach or restoreMocks: true in config

Async:

• Always return or await promises — an unawaited assertion can silently pass
• Use jest.useFakeTimers() for setTimeout/setInterval tests; always call jest.useRealTimers() in afterEach

Coverage:

• Set thresholds in jest.config.ts — don't chase 100%; target branches and functions
• /* istanbul ignore next */ — use sparingly with a comment explaining why

Never:

• it.only() or describe.only() merged to main — use --testNamePattern in dev
• Test implementation details — test behaviour observable from the outside
• Assertions inside loops — extract to helpers or use test.each

Related skills: Your frontend or backend layer (framework-specific setup), mocking/msw (HTTP mocking for integration tests)

Source: manikumarkv/devrunway-claude-plugin — distributed by TomeVault.