Integration Test & E2E Test Design/Implementation Rules Skill

Integration Test & E2E Test Design/Implementation Rules

Test Types and Limits

| Type | Purpose | File Format | Limit | |------|---------|-------------|-------| | Integration Test | Component interaction verification | *.int.test.ts | 3 per feature | | E2E Test | Critical user journey verification | *.e2e.test.ts | 1-2 per feature |

Critical User Journey: Features with revenue impact, legal requirements, or daily use by majority of users

Behavior-First Principle

Observability Check (All YES = Include)

| Check | Question | If NO | |-------|----------|-------| | Observable | Can user observe the result? | Exclude | | System Context | Does it require integration of multiple components? | Exclude | | Automatable | Can it run stably in CI environment? | Exclude |

Include/Exclude Criteria

Include: Business logic accuracy, data integrity, user-visible features, error handling Exclude: External live connections, performance metrics, implementation details, UI layout

Skeleton Specification

Required Comment Format

// AC: "[Acceptance criteria original text]"
// ROI: [0-100] | Business Value: [0-10] | Frequency: [0-10]
// Behavior: [Trigger] -> [Process] -> [Observable Result]
// @category: core-functionality | integration | edge-case | ux | e2e
// @dependency: none | [component name] | full-system
// @complexity: low | medium | high
it.todo('[AC number]: [Test name]')

Property Annotations

// Property: `[Verification expression]`
// fast-check: fc.property(fc.[arbitrary], (input) => [invariant])
it.todo('[AC number]-property: [Invariant description]')

ROI Calculation

ROI = (Business Value x Frequency + Legal Requirement x 10 + Defect Detection) / Total Cost

| Type | Total Cost | E2E Generation Condition | |------|------------|-------------------------| | Integration | 11 | - | | E2E | 38 | ROI > 50 |

Implementation Rules

Property-Based Test Implementation

When Property annotation exists, fast-check library is required:

import fc from 'fast-check'

it('AC2-property: Model name is always gemini-3-pro-image-preview', () => {
  fc.assert(
    fc.property(fc.string(), (prompt) => {
      const result = client.generate(prompt)
      return result.model === 'gemini-3-pro-image-preview'
    })
  )
})

Requirements:

Write in fc.assert(fc.property(...)) format
Reflect skeleton's // fast-check: comment directly in implementation
When failure case discovered, add as concrete unit test (regression prevention)

Behavior Verification Implementation

Behavior Description Verification Levels:

| Step Type | Verification Target | Example | |-----------|--------------------| --------| | Trigger | Reproduce in Arrange | API failure -> mockResolvedValue({ ok: false }) | | Process | Intermediate state or call | Function call, state change | | Observable Result | Final output value | Return value, error message, log output |

Pass Criteria: Pass if "observable result" is verified as return value or mock call argument of test target

Verification Item Determination Rules

| Skeleton State | Verification Item Determination Method | |----------------|---------------------------------------| | // Verification items: listed | Implement all listed items with expect | | No // Verification items: | Derive from "observable result" in "Behavior" description | | Both present | Prioritize verification items, use behavior as supplement |

Integration Test Mock Boundaries

| Judgment Criteria | Mock | Actual | |-------------------|------|--------| | Part of test target? | No -> Can mock | Yes -> Actual required | | Is call verification target of test? | No -> Can mock | Yes -> Actual or verifiable mock | | External network communication? | Yes -> Mock required | No -> Actual recommended |

Judgment Flow:

External API (HTTP communication) -> Mock required
Component interaction under test -> Actual required
Log output verification needed -> Use verifiable mock (vi.fn())
Log output verification not needed -> Actual or ignore

E2E Test Execution Conditions

Execute only after all components are implemented
Do not use mocks (@dependency: full-system)

Review Criteria

Skeleton and Implementation Consistency

| Check | Failure Condition | |-------|-------------------| | Property Verification | Property annotation exists but fast-check not used | | Behavior Verification | No expect for "observable result" | | Verification Item Coverage | Listed verification items not included in expect | | Mock Boundary | Internal components mocked in integration test |

Implementation Quality

| Check | Failure Condition | |-------|-------------------| | AAA Structure | Arrange/Act/Assert separation unclear | | Independence | State sharing between tests, execution order dependency | | Reproducibility | Depends on date/random, results vary | | Readability | Test name and verification content don't match |

Agent Skills: Integration Test & E2E Test Design/Implementation Rules

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