Build-an-X workflow that emits per-SW state-transition tests covering the six `ServiceWorkerState` values per [w3c-github-io/ServiceWorker][sw-spec] (`parsed → installing → installed → activating → activated → redundant`), the `install` / `activate` / `fetch` event handlers per [MDN Service Worker API][mdn-sw], `event.waitUntil()` lifetime extension, `ServiceWorkerGlobalScope.skipWaiting()` and `Clients.claim()` upgrade-path semantics, the `statechange` event on `ServiceWorker` objects, `ServiceWorkerRegistration.update()`, and `navigator.serviceWorker.controller` checks. Output: a Playwright spec file with one test per transition plus a clean upgrade-path test (v1 active → v2 installed/waiting → v2 activated, with claim()). The general Playwright SW harness, `service-worker-mock` unit tests, and cache-strategy assertions live in references/. Use when authoring the baseline lifecycle spec, when a deploy leaves users stuck on the old service worker, or when a site's caching / offline behavior is uncovered.

Builds a persistent flakiness infrastructure dashboard from JUnit XML or JSON CI run history: defines the flake-rate metric (failures per test over a configurable window), authors the data model, generates a Grafana time-series panel JSON or configures a Datadog CI Visibility view, derives the quarantine-candidate query, and wires trend alerts. Also generates the periodic (weekly / monthly) test-suite trend report - total runs, suite duration, flakiness rate, top failing tests, time-to-green per PR, week-over-week deltas - as a markdown summary for a team Slack channel or wiki page. Use when a team needs a long-lived observability surface for test reliability, or a scheduled comparable health report on top of it.

Author and run QEMU system emulation as an embedded-test target - qemu-system-arm / qemu-system-aarch64 / qemu-system-riscv32 launching cross-compiled ELF binaries on virtual MCUs and SoCs. Covers machine selection (-M virt / mps2-an385 / mps2-an386 / mps2-an500 / mps2-an511 / mps3-an524 / lm3s6965evb / raspi3b / xilinx-zynq-a9), CPU selection (-cpu cortex-m0 / cortex-m3 / cortex-m4 / cortex-m33 / cortex-a15 / cortex-a57 / max), -kernel ELF load, -nographic + -serial stdio, ARM semihosting via -semihosting-config enable=on,target=native (so cross-compiled GoogleTest / Unity binaries print to host stdio and exit with the test return code), GDB stub via -S -gdb tcp::1234, QMP monitor via -qmp tcp:host:port for automated test orchestration, and CI wiring. Use when host-only test runs are insufficient and the team wants arch-correct (endianness / alignment / interrupt-vector) behaviour on a virtual MCU without committing to physical hardware-in-loop.

Builds a release-readiness gate for a data pipeline by gathering check results from one or more engines (dbt, Great Expectations, Soda), applying severity-aware pass/fail thresholds, and emitting a single go / no-go decision with per-check rationale. Use when authoring a CI step that must fail the build when data quality drops below thresholds.

Build per-database MVCC isolation-level tests - Read Uncommitted vs Read Committed vs Repeatable Read vs Serializable; verify which anomalies are prevented at each level (dirty read, non-repeatable read, phantom read, serialization anomaly, write skew). Per PostgreSQL transaction isolation docs; analogous patterns for MySQL InnoDB, SQL Server, and DynamoDB. Use when two concurrent transactions can touch the same rows (balance debit, seat booking, stock decrement), or before changing a service's default isolation level.

Reference for the W3C ARIA Authoring Practices Guide (APG) - covers the 31 canonical interactive-widget patterns (Combobox, Dialog, Menu, Tabs, Tree, etc.), their required ARIA roles and states, the keyboard-interaction model per pattern, and the canonical-violations to watch for. Use when authoring a custom interactive widget that doesn't have a native HTML equivalent, or when reviewing one for ARIA correctness.