Testing Strategy

Comprehensive testing guidance for test architecture, coverage strategy, and test design.

Test Pyramid

Level Speed Cost Confidence Share

Unit ~1ms Low Narrow 65-80%

Integration ~100ms Medium Medium 15-25%

Contract ~10ms Low API shape Part of unit

E2E ~1s+ High Broad 5-10%

Key Principles

• Test behavior, not implementation — test what code does, not how

• Follow the testing pyramid — more unit tests, fewer E2E

• Use meaningful coverage metrics — branch coverage over line coverage

• Prevent flaky tests — no arbitrary waits, no test interdependence

Quick Start Checklist

• Choose test framework (Vitest recommended for new projects)

• Design test folder structure mirroring source

• Write unit tests for pure logic and utilities

• Add integration tests for API endpoints and data flows

• Add contract tests against OpenAPI spec (if applicable)

• Add E2E tests for critical user journeys only

• Set up CI to run tests on every PR

What NOT to Test

• Framework internals (React rendering, Express routing)

• Third-party library behavior

• Trivial getters/setters with no logic

• Implementation details (private methods, internal state)

References

Reference Description

test-architecture-structure.md Project structures, shared utilities, test configuration

test-architecture-isolation.md Playwright config, database isolation, performance optimization

test-design-techniques.md Equivalence partitioning, boundary values, decision tables, state transitions

test-design-error-and-advanced.md Error handling tests, property-based testing, parameterization, regression

frontend-react-testing.md React Testing Library, queries, user events, hooks, forms

frontend-vue-a11y-visual.md Vue Test Utils, accessibility, visual/Storybook testing, anti-patterns

e2e-playwright.md Playwright POM, fixtures, auth state, API mocking, visual comparison

e2e-cypress-and-stability.md Cypress patterns, flaky test prevention, test data, debugging

mocking-fundamentals.md Mock decision tree, stubs/mocks/spies/fakes, MSW setup and usage

mocking-modules-and-patterns.md Module mocking, time mocking, anti-patterns, dependency injection

coverage-guide.md Coverage metrics, meaningful thresholds, CI integration

api-test-frameworks-setup.md Vitest and Jest setup, configuration, running tests

api-test-supertest-and-helpers.md Supertest usage, request helpers, custom matchers, snapshots, debugging

api-integration-patterns.md CRUD endpoint tests, relationship tests

api-auth-patterns.md Login/logout, protected routes, authorization, auth helpers

api-e2e-and-edge-cases.md Multi-step workflow tests, error responses, edge cases

api-test-data-factories.md Factory patterns, builders, fixtures

api-test-data-database.md Database helpers, cleanup strategies, data generation

api-contract-openapi.md OpenAPI/AJV schema validation, contract tests

api-contract-zod-advanced.md Zod validation, response shape testing, breaking change detection

api-test-ci-pipelines.md CI pipeline strategy, GitHub Actions, parallel execution

api-test-ci-environments.md Environment config, test reporting, database services, E2E environments

anti-rationalization.md Iron Law, common rationalizations, red flag STOP list for TDD discipline