Integration and E2E Testing Principles
References
E2E test design with Playwright: See references/e2e-design.md for UI Spec-driven E2E test candidate selection and Playwright test architecture.
Test Type Definition and Limits
| Test Type | Purpose | Scope | Limit per Feature | Implementation Timing |
|---|---|---|---|---|
| Integration | Verify component interactions | Partial system integration | MAX 3 | Created alongside implementation |
| E2E | Verify critical user journeys | Full system | MAX 1-2 | Executed in final phase only |
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)
Exclude (Low ROI in CI/CD)
- External service real connections → Use contract/interface verification
- Performance metrics → Non-deterministic, defer to load testing
- Implementation details → Focus on observable behavior
- UI layout specifics → Focus on information availability
Principle: Test = User-observable behavior verifiable in isolated CI environment
ROI Calculation
ROI Score = (Business Value × User Frequency + Legal Requirement × 10 + Defect Detection)
/ (Creation Cost + Execution Cost + Maintenance Cost)
Cost Table
| Test Type | Create | Execute | Maintain | Total |
|---|---|---|---|---|
| Unit | 1 | 1 | 1 | 3 |
| Integration | 3 | 5 | 3 | 11 |
| E2E | 10 | 20 | 8 | 38 |
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 | e2e
// @dependency: none | [component names] | full-system
// @complexity: low | medium | high
// ROI: [score]
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 event → verify outcome |
| While | State condition | Setup state → verify behavior |
| If-then | Branch coverage | Both condition paths verified |
| (none) | Basic functionality | Direct invocation → verify result |
Test File Naming Convention
- Integration tests:
*.int.test.*or*.integration.test.* - E2E tests:
*.e2e.test.*
The test runner or framework in the project determines the appropriate file extension.
Review Criteria
Skeleton and Implementation Consistency
| Check | Failure Condition |
|---|---|
| Behavior Verification | No assertion for "observable result" in skeleton |
| Verification Item Coverage | Listed items not all covered by assertions |
| 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, order dependency |
| Reproducibility | Date/random dependency, varying results |
| Readability | Test name doesn't match verification content |
Quality Standards
Required
- Each test verifies one behavior
- Clear AAA (Arrange-Act-Assert) structure
- No test interdependencies
- Deterministic execution
Prohibited
- Testing implementation details
- Multiple behaviors per test
- Shared mutable state
- Time-dependent assertions without mocking