Integration E2E Testing

Integration Test & E2E Test Design/Implementation Rules

References

• references/e2e-design.md - E2E test design principles with Playwright (candidate properties, selection criteria, candidate record)
• references/e2e-environment-prerequisites.md - service-integration-e2e environment prerequisites (seed data, auth fixtures, environment checklist); fixture-e2e requires no live service or real database

Test Types and Selection

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
• Select service-integration-e2e when the proof obligation is real cross-service behavior such as data persistence, transactional consistency, or an external service contract

Start from accepted proof obligations, assign each to the cheapest boundary that can expose its failure, remove duplicate coverage, and keep the smallest set that covers every remaining distinct failure. Let those obligations determine the test count. A feature may validly produce no test in a lane.

Behavior-First Principle

Candidate Evidence

An integration/E2E candidate states:

• an observable result at the boundary named by the accepted behavior
• a material failure that crosses the components exercised by the selected lane
• an automated harness or controlled environment capable of reproducing that failure

Route behavior observable in isolation to unit/component verification. Record an unavailable controlled environment as a proof prerequisite for service-integration-e2e.

Candidate Routing

• Keep business-logic accuracy, data integrity, user-visible behavior, and observable error handling in the integration/E2E pool when they require those boundaries
• Route pure implementation details and data transformations to unit tests, performance claims to performance verification, and layout-only claims to visual or UI checks
• Represent external contracts with service-level stubs or a controlled local service when that contract is the proof target

Skeleton Specification

Required Skeleton Format

A committed file matching the project's test include pattern must remain valid to its runner. Use the detected framework's smallest pending suite (describe plus it.todo, or its equivalent), with only the test-framework import and the required comments. The implementing task replaces pending cases and adds application imports, assertions, fixtures, and mock setup alongside implementation.

Each test MUST include the following annotations.

// AC: "[Acceptance criteria original text]"
// Behavior: [Trigger] -> [Process] -> [Observable Result]
// @lane: integration | fixture-e2e | service-integration-e2e
// @dependency: none | [component names] | full-ui (mocked backend) | full-system
// @real-dependency: [component name] (optional, when Test Boundaries specify non-mock setup)
// Primary failure mode: [specific regression that must make the implemented test fail]
// Proof obligation: [boundary and observable state the implemented test must assert]
// Verification items: [observations that establish the obligation]

@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. @dependency is typically full-ui (mocked backend)
• service-integration-e2e — Browser-level or end-to-end verification against running local services or stubs. @dependency is full-system

Property Annotations

// Property: `[Verification expression]`
// fast-check: fc.property(fc.[arbitrary], (input) => [invariant])

Test Set Selection

1. Read the accepted behavior and each recorded proof obligation from the governing artifact or task.
2. For each obligation, name the material failure that must make a test fail and the observable state that exposes it.
3. Search existing tests. Reuse coverage only when it exercises the same boundary and would fail for that failure.
4. Assign the obligation to the narrowest sufficient lane:
   • unit/component when isolated execution exposes the behavior
   • integration for in-process component contracts
   • fixture-e2e for browser behavior whose backend may be deterministic
   • service-integration-e2e for persistence, transactions, messages, or external contracts whose failure is exposed only through that running boundary
5. Merge obligations when one scenario proves them while preserving a clear assertion-to-failure mapping. Keep distinct setup and failure modes in separate scenarios.
6. Emit only the remaining minimal covering set. Record the accepted behavior, primary failure, proof obligation, selected lane, and mock boundary in each skeleton.

Select from accepted behavior and repository proof boundaries; product analytics and numerical value estimates are unnecessary. Escalate when the accepted behavior or required contract remains unresolved after consulting governing sources and repository evidence.

Implementation Rules

Property-Based Test Implementation

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

• 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:

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