Configures StrykerJS for mutation testing of JavaScript / TypeScript / React / Vue / Svelte / Node - picks the test-runner plugin (`@stryker-mutator/jest-runner`, `mocha-runner`, `vitest-runner`, `karma-runner`), authors `stryker.conf.json` with mutate globs + thresholds, runs incremental mode for PRs (only mutate changed files), and reports the mutation score. Use when a JS/TS test suite has ≥80% line coverage and the team wants to verify the tests actually catch bugs (not just touch lines).
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Per stryker-intro:
"Stryker started as a pure JavaScript mutation testing framework" and now "supports most JavaScript projects, including TypeScript, React, Angular, VueJS, Svelte, and NodeJS."
Mutation testing introduces small bugs (mutants) into the production code; if tests still pass, the test suite is too weak. A green suite with high mutation-survival rate is the bug coverage hides.
.toBeTruthy() etc); mutation testing makes the cost visible.npm install --save-dev \
@stryker-mutator/core \
@stryker-mutator/jest-runner # or mocha-runner / vitest-runner / etc.
Per stryker-intro, supported runners include Jest, Mocha, Karma, Vitest, Jasmine, Cucumber, Tap.
npx stryker init
Generates stryker.conf.json:
{
"$schema": "./node_modules/@stryker-mutator/core/schema/stryker-schema.json",
"packageManager": "npm",
"reporters": ["progress", "clear-text", "html"],
"testRunner": "jest",
"coverageAnalysis": "perTest",
"mutate": ["src/**/*.ts", "!src/**/*.test.ts"],
"thresholds": { "high": 80, "low": 60, "break": 50 }
}
Key fields:
| Field | Use |
|---|---|
mutate | Glob patterns: which files to mutate; exclude tests + types. |
testRunner | jest / mocha / vitest / karma / etc. |
coverageAnalysis | perTest (fastest - only re-run tests that touched the mutated line). |
thresholds.break | Mutation score below this → npx stryker run exits non-zero (CI gate). |
incremental | true to only mutate files changed since last run. |
concurrency | Worker count (default = CPU count). |
npx stryker run
Per-mutant output:
[Survived] Conditional Boundary
src/cart.ts:42:5
- if (item.qty < 0) throw new Error(...);
+ if (item.qty <= 0) throw new Error(...);
Tests run: 12 (all passed - mutant survived).
Survived mutant = tests passed despite the introduced bug = the tests don't actually catch this regression. Add a test for qty = 0.
Ran 142 tests.
Mutants killed: 198
Mutants survived: 24
Mutants timed out: 3
Mutants no coverage: 12
Mutation score: 84.7%
Per stryker-intro: thresholds via the thresholds object
gate the build:
>= high (80) → green.>= low (60) → yellow.< break (50) → red, exit code != 0.The HTML report shows per-file mutation breakdown - drill in to see which mutants survived and where to add tests.
Full mutation runs are slow (5-30 min on medium codebases). For PRs, incremental mode only mutates changed files:
npx stryker run --incremental
This stores state in .stryker-tmp/ (commit to git so subsequent
runs benefit). Per-PR runs typically complete in <2 min.
- name: Mutation testing (changed files only)
if: github.event_name == 'pull_request'
run: npx stryker run --incremental
- name: Full mutation run
if: github.ref == 'refs/heads/main' && github.event.schedule == '0 2 * * 0'
run: npx stryker run
- uses: actions/upload-artifact@v4
if: always()
with:
name: stryker-report
path: reports/mutation/
Pattern: incremental on PRs (fast feedback) + full weekly run on main (catches drift in unchanged code).
| Anti-pattern | Why it fails | Fix |
|---|---|---|
Setting break: 100 | Impossible bar; team disables. | Start at 50-60; ratchet up over time. |
Running on every PR without --incremental | 30-min PR feedback loop; team disables. | --incremental for PRs (Step 5). |
| Mutating test files | Mutants in test code don't reflect production quality. | Exclude in mutate glob (Step 2). |
| Ignoring "no coverage" mutants | Files in mutate glob without any test coverage; mutation testing wastes effort. | Either add tests OR exclude those files from mutate. |
Using coverageAnalysis: off | Re-runs entire suite per mutant; very slow. | perTest (the default; Step 2). |
| Hard-coding break threshold without team agreement | Fails surprise PRs; team disables. | Land threshold via PR with team review. |
tsconfig.tsbuildinfo)
for mutation runs if not needed.stryker-net-mutation -
.NET sibling.pitest-mutation - Java sibling.mutmut-mutation - Python sibling.mull-mutation - C/C++ sibling.还没有评价。欢迎分享你的使用感受。
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Builds a CI gate that fails the build on **new** WCAG / a11y violations introduced by a PR while grandfathering pre-existing violations on a per-rule / per-page baseline. Aggregates verdicts from axe-core / pa11y / Lighthouse a11y / WAVE / IBM Equal Access scans. Use when a project has accumulated a11y debt and a strict "zero violations" gate would block every PR - the ratchet pattern lets the team ship while preventing regressions.
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Workflow skill that builds an A/B-test validity checklist from an experiment proposal, walking the canonical design-correctness gates - pre-registered OEC/power/guardrails, randomization unit + SRM check, assignment integrity, telemetry, peeking discipline, novelty/primacy, post-experiment SRM re-check - into a per-experiment checklist + sign-off form. Use when launching, auditing, or governing an experiment. For pitfall mechanics (guardrails, peeking) see experiment-results-interpreter's references; to read an already-valid result use experiment-results-interpreter; for per-SDK harness tests use experiment-sdk-testing - this gates DESIGN, not SDK code.
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The single install-flow skill: the reference contract for the PWA install flow (installability gate fields, `beforeinstallprompt` handshake, per-platform paths - Android WebAPK / iOS Share menu / Firefox no-op - and the `display-mode` post-install signal, in references/install-flow-reference.md) plus the build-an-X workflow that emits the Add-to-Home-Screen suite. Walks the four-stage timeline, emitting one test per gate cell per [web.dev/articles/install-criteria][install-criteria], the deferred-prompt → `prompt()` → `userChoice` chain per [web.dev/articles/customize-install][customize-install], the iOS Safari manual-metadata branch (`apple-touch-icon`) per [web.dev/learn/pwa/installation][learn-pwa], and the post-install `(display-mode: standalone)` MQ assertion. Output: a Playwright spec with per-stage cells plus a coverage matrix. Use when a PWA's manifest, icons, or install handler change, when install conversion drops at an unknown stage, or when triaging a flaky install assertion.
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Build-an-X workflow that uses an LLM to map existing tests to spec sections - given a spec doc + the test suite, the LLM identifies which tests cover which sections, surfaces uncovered sections (gap), and recommends specific tests to add. Output is a coverage matrix per spec ID. Scope is mapping tests that already exist and naming the gaps, not authoring tests for new acceptance criteria. Use when a spec doc and a test suite both exist but nobody can say which requirements are actually covered - before a release sign-off, an audit, or a decision about where to spend the next round of test effort.
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Generates tests from natural-language specs (acceptance criteria, user stories, requirements) using an LLM, with confidence scoring per test case (LLM self-assessment plus heuristics: assertion quality, naming, completeness), batching uncertain cases for human review, and integration with the team's existing test framework. Use when the user asks to generate unit tests from acceptance criteria, convert user stories to test cases, automate test creation from requirements, or augment a spec-driven test suite with AI-generated stubs that are then curated before merge.
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Configures Allure Report (test-runner adapter install, `allure-results` directory wiring, `categories.json` for failure classification, `history-trend.json` retention via the copy-history-between-runs pattern), runs the Allure CLI to convert `allure-results` to a static HTML site, and uploads the report as a CI artifact. Use when the team needs richer test reporting than JUnit XML - step-level attachments, per-test history, retry tracking, and severity / epic / feature labeling across framework-agnostic adapters (pytest, Jest, JUnit, TestNG, NUnit, Mocha). As a rich static HTML report generator, it is the open-source alternative to the sunset ExtentReports (JVM/.NET per-test HTML narrative); for hosted cross-run flakiness analytics rather than a static per-run report use currents-integration.
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