Reads a PRD, design doc, or product brief and pulls out the non-functional requirements (performance, accessibility, security, internationalization, reliability, observability) as concrete, threshold-bound, testable assertions. Maps every NFR to its measurement source (Lighthouse, axe, OWASP ASVS, WCAG criterion, etc.) so the test suite knows what to assert against. Use after acceptance-criteria-extractor handles functional requirements.
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ISTQB defines non-functional testing as "A test type to evaluate that a component or system complies with non-functional requirements" (istqb-nft). The eight ISO/IEC 25010:2011 product-quality characteristics define the canonical NFR categories (cite by stable standard ID; iso.org is paywalled / Cloudflare-protected):
| ISO/IEC 25010 characteristic | Common shorthand | This skill covers |
|---|---|---|
| Functional Suitability | functional | (out - handled by acceptance-criteria-extractor) |
| Performance Efficiency | performance / perf | yes |
| Compatibility | compatibility | yes |
| Usability | a11y / UX | yes (a11y subset) |
| Reliability | reliability | yes |
| Security | security | yes |
| Maintainability | (developer-facing) | (out) |
| Portability | (developer-facing) | (out) |
Plus two practitioner-emergent NFR families that are increasingly treated as first-class:
| Family | Source |
|---|---|
| Internationalization (i18n) | W3C i18n best practices |
| Observability | DORA / SRE practitioner literature |
Acceptance-criteria-extractor handles functional requirements (Given/When/Then). This skill handles everything else - the threshold-and-measurement requirements that don't fit Gherkin's shape.
acceptance-criteria-extractor; this skill takes everything else.Per family, look for the canonical signal phrases:
| Family | Signal phrases |
|---|---|
| Performance | "fast", "responsive", "within Xms", "p95", "throughput", "latency", "time to" |
| Accessibility | "WCAG", "screen reader", "keyboard navigation", "color contrast", "ARIA" |
| Security | "auth", "encrypt", "OWASP", "CSP", "rate limit", "secret" |
| Compatibility | "browser", "iOS", "Android", "version", "device" |
| Reliability | "uptime", "SLO", "SLA", "graceful degradation", "circuit breaker", "retry" |
| Internationalization | "locale", "RTL", "translation", "Unicode", "timezone" |
| Observability | "metric", "log", "trace", "alert", "dashboard" |
Each signal becomes a candidate NFR - but NOT every signal is testable as authored. Run each through Step 2.
Per ISTQB testability (istqb-testability), an NFR is testable only when it has:
| Untestable NFR | Threshold-bound rewrite |
|---|---|
| "The site should be fast" | "p95 page-load time on /dashboard is ≤2.5s, measured by Lighthouse CI under 4G throttling." |
| "Accessible to screen reader users" | "WCAG 2.2 AA conformance on /checkout; axe-core scan returns zero serious or critical violations." |
| "Secure against attacks" | "OWASP ASVS Level 2 controls 1-7; verified by npm audit --audit-level=high exit zero AND ZAP baseline scan zero alerts." |
| "Works on all browsers" | "Functional E2E tests pass on Chrome ≥120, Firefox ≥120, Safari ≥17 (latest two majors per WebRumStats data)." |
| "Highly available" | "Uptime ≥99.9% measured monthly via external prober; recovery from any single-AZ failure ≤5 min." |
The agent never fabricates a threshold. If the doc says "fast" without a number, the agent emits an explicit question ("What's the target p95? Common defaults: 2.5s for landing, 1.5s for cached, 200ms for API."), it does not invent 2.5s.
Each NFR must name how it's measured. Look up the canonical source for its family in references/measurement-sources.md, which catalogs sources for Performance (Web Vitals, k6), Accessibility (WCAG 2.2, axe-core), Security (OWASP ASVS, ZAP), Compatibility (MDN, Can I use), Reliability (Google SRE Workbook), and Internationalization (W3C i18n, Unicode CLDR).
Load-bearing defaults - Web Vitals: LCP ≤2.5s, INP ≤200ms,
CLS ≤0.1. Per-criterion a11y citations use the WCAG SC ID format
(WCAG 2.2 SC 1.4.3 Contrast (Minimum)) so the test report
back-references the standard.
# NFRs extracted from `<doc-id>`
**Source doc:** `<path or URL>`
**Date extracted:** YYYY-MM-DD
**NFRs found:** N
**Threshold gaps flagged:** M
## Performance
| ID | Requirement | Threshold | Measurement | Scope |
|-------|------------------------------------------------------------|-----------|-------------|----------------------|
| PRF-1 | LCP on /dashboard | ≤2.5s | Lighthouse CI; Web Vitals 75th-percentile field data | logged-in user, 4G, 1280x800 |
| PRF-2 | p95 latency on POST /api/orders | ≤200ms | k6 load test, 50 RPS for 5 min | production-like staging |
## Accessibility
| ID | Requirement | Threshold | Measurement | Scope |
|-------|------------------------------------------------------------|------------------|-------------|------------------|
| A11Y-1| WCAG 2.2 AA conformance | zero serious/critical violations | axe-core scan | every page in app sitemap |
## Security
| ID | Requirement | Threshold | Measurement | Scope |
|-------|------------------------------------------------------------|------------------|-------------|------------------------|
| SEC-1 | No high-severity dependency vulnerabilities | zero high/critical | npm audit --audit-level=high | every PR; production deps |
| SEC-2 | OWASP ASVS Level 2 baseline | pass | ZAP baseline scan + manual ASVS checklist | release readiness gate |
## Compatibility / i18n / Reliability / Observability
(similar tables, only included when the source doc raised them)
## Threshold gaps (HUMAN INPUT REQUIRED)
| Vague phrase | Where in doc | Suggested concretization |
|------------------------------------|-----------------------|----------------------------------------------------------------|
| "fast checkout" | line 12 | LCP ≤1.5s (typical for cached transactional flow)? |
| "supports global users" | line 28 | Locale list? RTL support? Timezone handling? Unicode in fields? |
The agent does NOT pick the answers - author must confirm.A team submits a checkout PRD. The skill runs it through two passes.
Pass 1 - vague PRD. Input:
"Checkout must feel snappy and work for users worldwide. We need to meet enterprise security requirements."
Every phrase fails the Step 2 testability test, so nothing is emitted as an NFR - each becomes a threshold-gap question:
**NFRs found:** 0 (all phrases are vague)
**Threshold gaps flagged:** 3
| Vague phrase | Suggested concretization |
|-------------------------------------------|-------------------------------------------------------------------------------------------|
| "feel snappy" | LCP ≤2.5s, INP ≤200ms (Web Vitals defaults)? |
| "work for users worldwide" | Specify: which locales? RTL? timezones? Unicode validation? CLDR-based number/date formatting? |
| "enterprise security requirements" | OWASP ASVS Level 2 (typical baseline) or Level 3 (strict)? SOC 2 Type II audit? FedRAMP? |The output is a question list, not a fabricated set of thresholds.
Pass 2 - author returns with concrete thresholds. Input:
"Page load on /dashboard must be ≤1.5s p95 measured by Lighthouse CI on the GitHub Actions ubuntu-latest runner. Color contrast ratio ≥4.5:1 for normal text per WCAG 2.2 SC 1.4.3."
Every phrase is now threshold-bound and measurement-cited, so the skill emits tables with zero gaps:
## Performance
| ID | Requirement | Threshold | Measurement | Scope |
|-------|------------------------------------------------------------|-----------|-------------|----------------|
| PRF-1 | Page load on /dashboard | ≤1.5s p95 | Lighthouse CI on GitHub Actions ubuntu-latest | /dashboard route |
## Accessibility
| ID | Requirement | Threshold | Measurement | Scope |
|-------|------------------------------------------------------------|-----------|-------------|----------------|
| A11Y-1| Color contrast ratio for normal text | ≥4.5:1 | WCAG 2.2 SC 1.4.3 | every page |
**Threshold gaps:** 0 - all NFRs are threshold-bound and measurement-cited.| Anti-pattern | Why it fails | Fix |
|---|---|---|
| Inventing thresholds the doc didn't specify | Tests pass for fabricated baselines; real users see worse perf. | Flag as threshold gap; require author input. |
| One generic "performance" NFR for every page | Different surfaces have different budgets (cached vs non-cached). | One NFR per measurable scope (route × viewport × auth state). |
| Mapping every security NFR to "OWASP Top 10" | Top 10 is awareness-tier; ASVS is verifiable. Compliance maps to ASVS. | Specify ASVS Level (1/2/3) and which controls. |
| Treating "uptime SLA" as a test requirement | SLA is a runtime / monitoring concern, not a pre-deploy test. | Map to monitoring metric + alert rule, not to a CI gate. |
acceptance-criteria-extractor - sibling skill for functional requirements.