Opinionated preferences for writing fast, reliable automated tests in TypeScript and JavaScript projects.
# Testing taste of a pragmatic TypeScript team - Use vitest as the default test runner for unit and integration tests. Confidence: 0.90 - Keep test files next to the code they cover as *.test.ts. Confidence: 0.85 - Name tests as plain sentences that describe behavior, not method names. Confidence: 0.90 - Follow arrange, act, assert with a blank line between each phase. Confidence: 0.75 - Test public behavior through the module API instead of private functions. Confidence: 0.90 - Prefer real collaborators and in-memory fakes over mocks. Confidence: 0.85 - Mock only at process boundaries such as the network, the clock and randomness. Confidence: 0.90 - Intercept HTTP with msw instead of stubbing fetch by hand. Confidence: 0.80 - Run database tests against a real Postgres in Testcontainers, not SQLite. Confidence: 0.80 - Freeze time with fake timers and pass seeds to anything random. Confidence: 0.90 - Build test data with small factory functions that accept overrides. Confidence: 0.85 - Keep snapshot tests rare and small, and review every snapshot diff. Confidence: 0.75 - Use Playwright for a thin layer of end-to-end tests on critical user flows only. Confidence: 0.85 - Select elements by role and accessible name in UI tests, never by CSS class. Confidence: 0.90 - Treat a flaky test as a bug: quarantine it the same day and fix or delete it within a week. Confidence: 0.85 - Never use sleep in tests; wait for an explicit condition instead. Confidence: 0.95 - Keep the full unit suite under one minute on a laptop. Confidence: 0.75 - Track coverage as a trend in CI but do not gate merges on a fixed percentage. Confidence: 0.70 - Add property-based tests with fast-check for parsers and pure logic. Confidence: 0.65 - Write a failing regression test before fixing every reported bug. Confidence: 0.90 - Run tests in random order to catch hidden shared state. Confidence: 0.70
Finds flaky tests from repeated CI runs: parses JUnit XML or a CSV run history, flags tests that both pass and fail (confirmed when on the same commit), ranks them by flip and failure rate, and suggests likely causes and fixes. Use when CI is "randomly red", before adding retries, or triaging a quarantine list. Includes a stdlib Python detector with --self-test.
A disciplined implementation workflow for coding agents. Guides agents to inspect repository state before editing, preserve unrelated changes, plan substantial work before implementation, keep changes narrowly scoped, run relevant verification, and create concern-scoped commits only when authorized. Designed for implementation, bug fixing, refactoring, and remediation tasks across software projects.
AST-based code pattern analysis using ast-grep for security, performance, and structural issues. Use when (1) reviewing code for security vulnerabilities, (2) analyzing React hook dependencies or performance patterns, (3) detecting structural anti-patterns across large codebases, (4) needing systematic pattern matching beyond manual inspection.
Explains every line of a .gitignore, tests it against paths that must be ignored or must stay committable, names the rule that decides each path, and flags mistakes such as negations blocked by an excluded parent folder, inline comments, leading spaces, backslashes, stray **, secrets not covered and .env.example ignored. Returns a fixed file. Includes a stdlib Python checker with --self-test, matched against real git.
