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name: integration-e2e-testing description: Integration and E2E test design principles, ROI calculation, test skeleton specification, and review criteria. Use when designing integration tests, E2E tests, or reviewing test quality.

Integration and E2E Testing Principles

References

E2E test design: See references/e2e-design.md for UI Spec-driven E2E test candidate selection and browser test architecture. The reference uses Playwright as the default browser harness; substitute the project's standard when different.

Test Type Definition and Standard Budgets

| Test Type | Purpose | Scope | External Deps | Standard Budget per Input Design Doc | Implementation Timing | |-----------|---------|-------|---------------|-------------------|----------------------| | Integration | Verify component interactions in-process | Partial system integration (in-process modules; for UI components, the framework's in-process renderer e.g., RTL+MSW for React/TS) | Mocked or in-process | MAX 3 | Created alongside implementation | | fixture-e2e | Verify UI behavior in a browser with deterministic fixtures | Full UI flow with mocked backend / fixture-driven state | Mocked / fixture only — no live services | MAX 3 | Created alongside the UI feature | | service-integration-e2e | Verify critical user journeys against a running local stack | Full system across services | Live local services or stubs | MAX 1-2 | Earliest task where the proof boundary and required services are executable |

Lane selection (E2E only):

• Default lane for user-facing UI journeys is fixture-e2e — it runs a real browser against deterministic fixtures, catches the bugs that unit/integration tests miss (button no-op, state never updates, navigation breaks), and runs in CI without infrastructure setup
• Add service-integration-e2e only when the journey's correctness depends on real cross-service behavior (data persistence, transactional consistency, external service contracts) that cannot be faked safely

One input Design Doc is one budget scope: apply each lane budget once across all ACs and candidates in that document. The two E2E lanes are budgeted independently — having a fixture-e2e for a journey does not consume the service-integration-e2e budget and vice versa. Treat the numbers above as enforced standard budgets. Exceed a budget only when an accepted requirement or a distinct failure mode cannot be proved by a selected test; annotate that exception and why consolidation cannot cover it.

Behavior-First Principle

Include (High ROI)

• Business logic correctness (calculations, state transitions, data transformations)
• Data integrity and persistence behavior
• User-visible functionality completeness
• Error handling behavior (what user sees/experiences)

Redirect to Other Test Types

• External service connections → Verify via contract/interface tests
• Performance metrics → Verify via dedicated load testing
• Implementation details → Verify observable behavior instead
• UI layout specifics → Verify information availability instead

Principle: Test = User-observable behavior verifiable in isolated CI environment

ROI Calculation

ROI is used to rank candidates within the same test type (integration candidates against each other, E2E candidates against each other). Cross-type comparison is unnecessary because integration and E2E budgets are selected independently.

For every candidate, record the governing evidence for each ROI input before assigning a value. Use an approved PRD, confirmed requirement context, accepted contract or legal obligation, user-confirmed test value context, Design Doc boundary, and existing-test evidence as applicable. A missing value is unknown, not 0, and an inference is not observed evidence.

When ROI can change candidate ranking, a lane threshold, or budget selection, return the exact missing product input and its decision effect when test_value_context has not yet supplied it. After that single input round, apply the supplied facts and retain every remaining value as decision-relevant unknown with its numeric score unset. Resolve Defect Detection from repository evidence at the proof boundary and in existing tests. When selection is invariant because the candidate is removed before ROI, is the sole eligible candidate for a reserved journey slot, or all surviving candidates fit an unthresholded budget, record the unknown as not_decision_relevant and keep its numeric score unset.

Unknown-Value Ordering

For candidates with a decision-relevant unknown after the value-input round, use accepted legal or contractual obligation, explicit connection to the confirmed user or business outcome, distinct Defect Detection evidence, lower lane ownership cost, then source AC order. Select the smallest set that proves the accepted obligations and confirmed outcome boundaries, within the normal lane budgets. Numeric lane thresholds apply to fully scored candidates; this evidence ordering supplies the selection decision for affected candidates. Record the unknown input, evidence checked, and selection effect.

For resolved numeric inputs, use exactly 0, 5, or 10. Legal Requirement remains boolean; a governing-source check that finds no accepted legal, regulatory, contractual, or audit obligation supports false and records that checked source.

| Input | Scale | |---|---| | Business Value | 0 = no user/business outcome; 5 = meaningful but non-critical outcome; 10 = core, revenue, safety, or data-integrity outcome | | User Frequency | 0 = unreachable/obsolete; 5 = regular subset of users or runs; 10 = dominant journey or execution path | | Legal Requirement | true only when an accepted legal, regulatory, contractual, or audit requirement applies; otherwise false | | Defect Detection | 0 = duplicates existing proof; 5 = covers a distinct branch/state; 10 = uniquely detects a critical boundary or cross-service failure |

ROI Score = Business Value × User Frequency + Legal Requirement × 10 + Defect Detection
              (range: 0–120)

Higher ROI Score = higher priority within its test type. For equal scores, order by Legal Requirement (true first), then higher Defect Detection, Business Value, User Frequency, and finally source AC order. No normalization or capping is applied — the raw score is used directly for ranking. Deduplication is a separate step that removes candidates entirely; it does not modify scores.

ROI Thresholds by Lane

The two E2E lanes have different ownership costs and use independent standard thresholds.

| Lane | ROI threshold | Rationale | |------|---------------|-----------| | fixture-e2e | ROI ≥ 20 (beyond reserved slot) | Cost is comparable to integration tests once the harness exists; the floor avoids filling MAX 3 with low-signal tests when fewer would suffice | | service-integration-e2e | ROI > 50 (beyond reserved slot) | Live-service setup, state cleanup, and failure diagnosis add material ownership cost; reserve for journeys whose value cannot be proven any other way |

Reserved slot rules (see Multi-Step User Journey Definition below) apply per lane and override the threshold (the reserved candidate is emitted regardless of its ROI score). Emit a below-floor candidate beyond the reserved slot only when an accepted requirement or a distinct uncovered failure mode justifies the exception. Leave budget intentionally unfilled rather than padding with low-value tests; record any threshold or budget exception in the skeleton that carries the exception.

ROI Calculation Examples

| Scenario | BV | Freq | Legal | Defect | ROI Score | Test Type | Selection Outcome | |----------|----|------|-------|--------|-----------|-----------|-------------------| | Core checkout UI flow | 10 | 10 | true | 10 | 120 | fixture-e2e | Selected (reserved slot: user-facing multi-step journey, browser-level verification with fixtures) | | Core checkout against live payment service | 10 | 10 | true | 10 | 120 | service-integration-e2e | Selected (real-service correctness above ROI threshold) | | Dismiss button updates UI state | 5 | 10 | false | 5 | 55 | fixture-e2e | Selected (rank 2 of 3 fixture-e2e budget) | | Payment error message display | 5 | 5 | false | 5 | 30 | fixture-e2e | Selected (rank 3 of 3 fixture-e2e budget) | | Optional filter toggle | 5 | 5 | false | 0 | 25 | fixture-e2e | Removed during deduplication (duplicates existing proof) | | Payment retry against real provider | 5 | 5 | false | 5 | 30 | service-integration-e2e | Below ROI threshold (30 < 50), not selected | | DB persistence check | 10 | 5 | false | 10 | 60 | Integration | Selected (rank 1 of 3) | | Pure data transformation | 5 | 5 | false | 5 | 30 | Unit | Not selected (push down to unit test) |

Multi-Step User Journey Definition

A candidate qualifies as a multi-step user journey when ALL of the following are true:

1. 2+ distinct interaction boundaries are traversed in sequence to complete a user goal. What counts as a boundary depends on the system type:
   • Web: distinct routes/pages
   • Mobile native: distinct screens/views
   • CLI: distinct command invocations or interactive prompts
   • API: distinct API calls forming a transaction (e.g., create → confirm → finalize)
2. State carries across steps — data produced or actions taken in one step affect what the next step accepts or displays
3. The journey has a completion point — a final state the user or caller reaches (e.g., confirmation page, saved record, API success response, completed workflow)

User-Facing vs Service-Internal Journeys

Multi-step journeys are classified for reserved-slot eligibility:

| Classification | Condition | Reserved Slot Eligibility | Example | |---|---|---|---| | User-facing | A human user directly triggers and observes the steps (via UI, CLI, or direct API interaction) | Eligible — defaults to fixture-e2e reserved slot. Add a service-integration-e2e reserved slot only when the journey's correctness depends on real cross-service behavior | Web checkout flow, CLI setup wizard, mobile onboarding | | Service-internal | Steps are triggered by backend services without direct user interaction | Not eligible for reserved slot — use integration tests. Service-integration-e2e through normal ROI > 50 path is still valid when full-system verification is warranted | Async job pipeline, service-to-service saga, scheduled batch processing |

This classification applies only to the reserved-slot rule and the E2E Gap Check. Other selection follows lane-specific ROI rules above.

Use this definition when evaluating E2E test candidates and E2E gap detection.

Test Skeleton Specification

Required Comment Patterns

Each test MUST include the following annotations:

AC: [Original acceptance criteria text]
Behavior: [Trigger] → [Process] → [Observable Result]
@category: core-functionality | integration | edge-case | fixture-e2e | service-integration-e2e
@lane: integration | fixture-e2e | service-integration-e2e
@dependency: none | [component names] | full-system
@complexity: low | medium | high
ROI: [score]

@lane selection rule:

• integration — Component interaction in-process, no browser (e.g., RTL+MSW for React/TS, in-process module/handler integration in any language)
• fixture-e2e — Browser-level UI verification with mocked backend / fixture-driven state
• service-integration-e2e — Browser-level or end-to-end verification against running local services or stubs

Use the project's comment syntax to wrap these annotations (e.g., // for C-family, # for Python/Ruby/Shell).

Verification Items (Optional)

When verification points need explicit enumeration:

Verification items:
- [Item 1]
- [Item 2]

EARS Format Mapping

| EARS Keyword | Test Type | Generation Approach | |--------------|-----------|---------------------| | When | Event-driven | Trigger ev