qa

Use when a project has accessibility debt and a zero-violations gate would block every PR. Builds a CI ratchet that fails only on new WCAG violations a PR introduces, with pre-existing ones baselined per rule and page, from axe-core, pa11y, Lighthouse, WAVE or IBM Equal Access results.

Use when launching, auditing or governing an A/B test or online experiment design. Builds a per-experiment checklist and sign-off: pre-registered metric, power and guardrails, randomization unit and sample ratio mismatch checks, assignment, telemetry, peeking rules and novelty effects.

Use when a spec and a test suite both exist but nobody can say which requirements are covered, before a release sign-off, an audit or planning test effort. Uses an LLM to map existing tests to spec sections, outputs a coverage matrix per spec ID and names the gaps. It does not write new tests.

Use when tests should be generated from acceptance criteria, user stories or requirements with an LLM. Scores confidence per test case (self-assessment plus assertion, naming and completeness checks), batches uncertain cases for human review and emits tests in the team's existing framework.

Use when an existing API test suite should be rerun under network faults to prove retries, timeouts, circuit breakers and fallbacks work. Injects latency, timeouts, dropped connections, bandwidth caps and packet loss with Toxiproxy and reports which assertions break under which fault.

Use when building or reviewing a custom interactive widget with no native HTML equivalent (combobox, dialog, menu, tabs, tree and more). Gives the W3C ARIA Authoring Practices pattern: required roles and states, keyboard interaction and common violations.

Test async ordering - event-loop / queue / channel ordering assertions, JS Promise microtask vs macrotask ordering, Python `asyncio.gather` vs `asyncio.wait_for` semantics, Go goroutine + channel happens-before relationships, async/await re-entrancy. Use deterministic schedulers (sinon fake timers, asyncio test mode) to remove run-to-run variance. Use when a callback fires twice, a later response overwrites an earlier one, or a cancelled parent task leaves a child still running - bugs where completion order, not shared memory, is the defect.

Use when a team wants declarative, Terraform-style database schema management or migration linting beyond Flyway and Liquibase: Atlas schema apply, migrate diff against a dev database, migrate lint for destructive or locking changes, and migrate hash, across a dozen databases.

Use when audit logs need tests for HIPAA, PCI DSS, SOC 2, GDPR or another framework: the required events (logins, privilege changes, data access, admin actions, exports), structured log format, tamper-evident hash chains, immutability and retention, and replaying logs for forensics.

Use when an app uses Auth0 and needs tests for its tenant config, login flows or Action scripts: per-PR or namespaced tenants, Universal Login, PKCE, client credentials, Rules and Hooks, and config drift with a0deploy. Generic OAuth flows are oauth-flow-test-author.

Use whenever pages or components need automated accessibility scanning: axe-core via axe.run(), @axe-core/playwright or the CLI on every PR, rule configuration and CI-gateable results, plus pa11y, Lighthouse CI accessibility, WAVE and IBM Equal Access (Section 508) in its references.

Use whenever the code under test is a shell script, a CLI binary or anything run from Bash: argument parsing, flags, exit codes and output. Sets up Bats-core with @test blocks, run, status and output assertions, setup/teardown, shared helpers and TAP output for CI.

Use when a Cucumber, Behave or Reqnroll project has grown past ~50 step definitions, before writing a step that may already exist, or when new .feature files need a duplicate check. Inventories steps, merges duplicates, publishes a step-library README and a scenario coverage map.

Use when a Python project wants BDD scenarios with Behave: Gherkin .feature files, step implementations in features/steps, environment.py hooks, tags and behave runs in CI. The Python member of the Cucumber family.

Use when someone reports a problem informally, a CI failure (JUnit XML, Allure, pytest or Playwright output) must become a bug report, or a draft needs a quality check before filing. Fills summary, environment, steps, expected vs actual and severity rationale, then checks each field is usable.

Use when defect counts or reports are wrong (missing top-severity bugs, fixed items counted as new, unmerged duplicates) or bug filing and transitions need automating. One workflow for Jira, Linear, GitHub Issues and Azure DevOps: dedupe before filing, severity vs priority, lifecycle and CI filing.

Use whenever a Node.js or TypeScript service uses BullMQ and its queues or workers need tests: producers, worker processors, retries, backoff and repeat jobs, FlowProducer parent-child jobs and QueueEvents, against real Redis (Docker, Testcontainers) or ioredis-mock.

Pure-reference catalog of cache-coherence patterns across the request path. Defines the five-tier cache stack (browser → CDN → reverse-proxy → application → data store), the per-tier cache-writing patterns (cache-aside, write-through, write-back, write-around, refresh-ahead), and the canonical invalidation strategies (TTL-only, event-driven purge, surrogate keys, version-tagged URLs, soft purge), plus an anti-pattern table and a worked multi-tenant coherence-test example. Deep detail lives in references/: RFC 9111 Cache-Control / Vary / ETag directive tables, the cross-tier test surface, cache-stampede (thundering-herd) mitigations incl. the XFetch formula, and RFC 5861 stale-while-revalidate / stale-if-error semantics. Use for pattern selection, Cache-Control header design, coherence audits, stampede-refresh strategy, and SWR/SIE window design; use a cache-key-collision check when the question is whether two concrete requests collide on a key scheme.

Use whenever a user saw another user's or tenant's data, or a per-user response goes through a shared cache, Redis or a CDN, or a cache key is designed or changed. Checks the key holds every value the response depends on (tenant, user, scope, locale), writes the fixed key, Vary header and tests.

Use when CDN or browser caching needs tests: purges and invalidations on Cloudflare, Fastly (surrogate keys) and CloudFront, end-to-end write, purge and fresh-read checks, propagation delay and cache-status headers, plus browser Cache-Control, ETag and service-worker caching with Playwright.