accelint-ts-testing_skill

Overview

This skill provides comprehensive Vitest testing guidance tailored for TypeScript projects. It focuses on writing clear, fast, and reliable tests using AAA, parameterized tests, async/await patterns, and property-based testing with fast-check. The guidance prioritizes maintainability, correctness, and measurable improvements to test suites and reviews.

How this skill works

The skill inspects test files and project configuration to locate common anti-patterns and opportunities for stronger tests. It recommends config-level fixes (global mock cleanup), file-level organization, assertion improvements, test-double selection, async patterns, and where to apply fast-check properties like roundtrip and idempotence. When invoked for audits, it produces structured findings and actionable fixes using a standard report template.

When to use it

• Writing new tests in *.test.ts with Vitest (use AAA, it.each, strict assertions)
• Reviewing or auditing test code for anti-patterns (loose assertions, over-mocking, deep describe nesting)
• Optimizing slow test suites or configuring global mock cleanup in vitest.config.ts
• Implementing property-based tests with fast-check for encode/decode, validators, and idempotence checks
• Converting duplicated tests into parameterized cases or simplifying complex setup

Best practices

• Set clearMocks/resetMocks/restoreMocks in vitest.config.ts to avoid cross-test leaks
• Prefer testing observable behavior over implementation details; avoid counting internal calls
• Use strict assertions (deep equality, specific value checks) instead of toBeTruthy/toBeDefined
• Mock only external dependencies; prefer fakes > stubs > spies > mocks for stability
• Limit describe nesting to two levels and use descriptive test names for context
• Use fast-check to assert strong properties: roundtrip(encode/decode), idempotence(normalize)

Example use cases

• Convert several similar test cases into a single it.each parameterized test
• Audit a repository to add global mock cleanup and identify flaky tests caused by shared state
• Replace toBeTruthy assertions with precise shape or value checks to catch regressions
• Add property-based tests for an encode/decode pair to catch edge-case inputs
• Speed up suite by replacing real DB calls with in-memory fakes and mocking timers