Mutation testing (@tao.js/router)

Run

pnpm test:mutation:router

Reports in reports/mutation/ (gitignored). Use // Stryker disable … : reason for equivalents.

Notes

• Config: stryker.config.json — inPlace: true; barrel index.js excluded.
• jest.config.js sets testEnvironment: 'jsdom' explicitly — Stryker's perTest coverage analysis does not merge the preset-provided testEnvironment.
• Disable equivalent mutants with // Stryker disable … : reason (colon required).
• Equivalents disabled as unobservable, given this package's actual call sites:
  • capitalize's !str || typeof str !== 'string' guard (Router.js) — str is always undefined or a string captured from a URL path segment, never a truthy non-string, so !str alone (or forcing the guard true/false) can't diverge from the full guard.
  • reactToRoute's debug = false default parameter (Router.js) — every internal caller always passes an explicit boolean, so the default is never evaluated.
  • Detach's node.defaultData && node.defaultData.has(...) guard (Router.js) — Attach always initializes defaultData together with attached, so by the time Detach's outer attached.length guard is true, defaultData is always truthy too.
  • The if (incoming.length) guard (Router.js) — [].forEach(...) is already a no-op, so forcing entry into the block changes nothing observable when incoming is empty.
  • routeHandler.js's needData == null guard — path-to-regexp's compiled path function throws the identical Expected "..." to be a string error whether a param is omitted, null, or undefined.
  • routeTag.js's { default: '' } lookup option — the final route.join('') already converts a missing/undefined value to '', identical to the explicit default.
• Optional debug && console.log(...) logging paths are Stryker-disabled as equivalent (side-effect-only, not part of the observable contract), matching the convention used across this monorepo's other packages.
• Latest score (2026-07-18): 100% (271 killed, 0 timeout, 0 survived; thresholds high=95, low=90).