CRUSSPIC STMPL - Bach's quality-criteria mnemonic

Deep reference for exploratory-testing SKILL.md. CRUSSPIC STMPL is James Bach's quality-criteria mnemonic. The thirteen criteria are enumerated under "Quality Criteria Categories" in Bach's Heuristic Test Strategy Model (HTSM v6.3, 2024-11-05), which defines a quality criterion as "some requirement that defines what the product should be" (HTSM). The HTSM prints the criteria as named categories; the CRUSSPIC STMPL letters are the memory aid taught over them, not an acronym the HTSM itself spells out.

It overlaps with ISO/IEC 25010:2023 (the formal software- quality model) but offers a more practitioner-friendly mnemonic form that fits in an exploratory tester's working memory.

This reference is used when shaping a session's evaluation lens, and by the product-risk-register workflow (in qa-process's risk-matrix references/) when categorising risks by quality characteristic.

When to use

• Authoring a charter - pick which quality criteria the session will evaluate.
• Categorising risks in the product register (the product-risk-register reference of qa-process's risk-matrix).
• Evaluating a vendor / framework (framework-choice-advisor in qa-process, including its vendor-evaluation reference).
• Reviewing a release candidate - walk CRUSSPIC STMPL to confirm each criterion is addressed.

The thirteen criteria

CRUSSPIC - primary criteria

C - Capability

Does the system do what's claimed?

Functional correctness - the product performs its stated functions. Maps to ISO/IEC 25010 "Functional suitability."

Test heuristics: HICCUPPS-F's Claims oracle (hiccupps-f.md)

• Coverage from FCC CUTS VIDS (fcc-cuts-vids.md).

R - Reliability

Does the system work consistently over time?

• Mean Time Between Failures (MTBF)
• Fault tolerance (degraded mode, retry, failover)
• Recovery time + data preservation
• Idempotency under retry

Maps to ISO 25010 "Reliability."

U - Usability

Can the user figure out how to use it?

• Learnability for new users
• Efficiency for repeat users
• Memorability after time away
• Error-recovery from mistakes
• Satisfaction (qualitative)

Per Nielsen's usability heuristics.

S - Security

Is the system safe from misuse?

• Confidentiality (PII / secrets not exposed)
• Integrity (data not modified by attackers)
• Availability (DoS resistance)
• Authentication + authorization
• Auditability

Maps to ISO 25010 "Security." Composes with qa-security-scanning, qa-test-data-privacy.

S - Scalability

Does the system grow with load?

• Vertical scaling (bigger machines)
• Horizontal scaling (more machines)
• Data-volume scaling (more rows, bigger blobs)
• User-count scaling (more concurrent users)

Composes with qa-load-testing.

P - Performance

Is the system fast enough?

• Response latency (p50, p95, p99)
• Throughput
• Resource efficiency (CPU, memory, network, disk)
• Startup / cold-start time

Distinct from Scalability - performance is "fast for the user"; scalability is "still fast when load grows." Composes with qa-load-testing.

I - Installability

Can the user install + configure the system?

• Installer / setup wizard quality
• Configuration documentation
• Default values appropriate
• Upgrade path from prior versions
• Uninstall completeness

Maps to ISO 25010 "Portability - Installability."

C - Compatibility

Does the system work alongside other things?

• OS / browser compatibility matrix
• Backwards-compatibility (old data, old clients)
• Forwards-compatibility (newer data, newer clients)
• Coexistence (same machine, same network, with other software)
• Interoperability (API consumers)

Maps to ISO 25010 "Compatibility."

STMPL - secondary (operational) criteria

S - Supportability

Can the support team diagnose + fix issues?

• Log quality (useful, structured, searchable)
• Observability (traces, metrics)
• Self-service support materials (knowledge base)
• Escalation paths
• Reproducibility from logs alone

T - Testability

Can the testers verify the system?

• Test hooks / instrumentation
• Deterministic-mode toggles
• State-inspection endpoints
• Test-data-management hooks
• Mock-able external dependencies

M - Maintainability

Can the team change the system?

• Code clarity / structure
• Documentation
• Test coverage
• Dependency management
• Tech debt accumulation

Maps to ISO 25010 "Maintainability."

P - Portability

Can the system move between environments?

• Cloud-provider portability (AWS / GCP / Azure)
• OS portability
• Container / VM portability
• Data portability (export + import)
• Configuration portability

Maps to ISO 25010 "Portability."

L - Localizability

Can the system be adapted to other languages + cultures?

• Translation support
• Right-to-left layout
• Locale-specific formatting (dates, numbers, currency)
• Cultural appropriateness (icons, colours, idioms)
• ICU MessageFormat / plural rules

Composes with qa-localization.

Mapping to ISO/IEC 25010

ISO 25010 has 8 top-level characteristics:

CRUSSPIC STMPL is more granular; ISO 25010 is more formal. The two are complementary, not substitutable. Per ISO/IEC 25010:2023 (cite by stable ID).

Worked example - applying CRUSSPIC STMPL to a release review

Pre-release review:

## Release v3.0 quality-criteria walkthrough

- **C - Capability:** Functional acceptance tests 98% pass. ✓
- **R - Reliability:** Last 30 days uptime 99.94% (SLA: 99.9%). ✓
- **U - Usability:** User research session N=8; 7/8 completed
  signup without help (target: 6/8). ✓
- **S - Security:** Last pen-test 2026-03; all critical findings
  fixed; SAST + DAST clean. ✓
- **S - Scalability:** k6 load test at 10x expected peak passed
  with p99 < 800ms. ✓
- **P - Performance:** p95 latency 220ms (target 300ms). ✓
- **I - Installability:** New install flow 5 steps; user testing
  4/5 completed. ✓
- **C - Compatibility:** Browser matrix Chrome / Firefox / Safari
  all current + N-1 tested. ✓
- **S - Supportability:** All log lines structured; trace IDs
  end-to-end. ✓
- **T - Testability:** E2E suite runs in 18 min; deterministic
  mode available. ✓
- **M - Maintainability:** Sonar tech-debt rating A. ✓
- **P - Portability:** Cloud-portable (Terraform); no AWS-specific
  primitives. ✓
- **L - Localizability:** All UI strings extracted to ICU
  messages; 7 locales supported. ✓

Verdict: cleared for release.

Anti-patterns

Limitations

• Subjective weighting. Criteria importance differs per product / domain / regulatory context.
• Some criteria are evaluatable only in production. Reliability
  • Supportability need real usage data.
• Mnemonic overload. Thirteen letters is at the edge of working memory; testers often print the catalog.
• Doesn't replace ISO 25010 formal model. For regulated / compliance contexts use ISO 25010 + cite formally; use CRUSSPIC STMPL as the working-memory mnemonic.

References

• Bach J. Heuristic Test Strategy Model v6.3 (PDF), "Quality Criteria Categories" - the source enumerating the thirteen criteria this mnemonic indexes - satisfice.com/download/heuristic-test-strategy-model.
• Bach J. Heuristics of Software Testability - satisfice.com/heuristics-of-software-testability.
• ISO/IEC 25010:2023 "Systems and software Quality Requirements and Evaluation (SQuaRE) - Product quality model" - cite by stable ID; iso.org paywall.
• Nielsen J. Usability heuristics - nngroup.com/articles/ten-usability-heuristics.
• Sibling references: hiccupps-f.md, sfdpot.md, fcc-cuts-vids.md, tours.md.
• Consumed by: the product-risk-register workflow in qa-process's risk-matrix references/.