Shell Testing Framework

Validate test effectiveness with mutation testing using Stryker (TypeScript/JavaScript with Vitest or bun test via @hughescr/stryker-bun-runner) and mutmut (Python). Find weak tests that pass despite code mutations. Use to improve test quality.

Expert testing decision trees for GdUnit4: unit vs scene vs CI gates, headless runners, snapshots, and mock networks. Use when choosing test layers, wiring CI, or validating signals/physics without beginner assert catalogs. Keywords: GdUnit4, GdUnitTestSuite, headless CI, snapshot test, mock network, scene integration test, TDD.

Comprehensive vitest testing guidance for TypeScript projects. Use when (1) Writing new tests with AAA pattern, parameterized tests, or async/await, (2) Reviewing test code for anti-patterns like loose assertions (toBeTruthy), over-mocking, or nested describe blocks, (3) Optimizing slow test suites, (4) Implementing property-based testing with fast-check - especially for encode/decode pairs, roundtrip properties, validators, normalizers, and idempotence checks. Covers test organization, assertions, test doubles hierarchy (fakes/stubs/mocks), async testing, performance patterns, and property-based testing patterns. Trigger keywords on vitest, *.test.ts, describe, it, expect, vi.mock, fast-check, fc.property, roundtrip, idempotence.

Comprehensive TDD patterns and practices for all programming languages, eliminating redundant testing guidance per agent.

Automated accessibility testing with axe-core, Playwright, and jest-axe for WCAG compliance. Use when adding or validating a11y tests, running WCAG checks, or auditing UI accessibility.

Jest testing patterns, factory functions, mocking strategies, and TDD workflow. Use when writing unit tests, creating test factories, or following TDD red-green-refactor cycle.