Frontend Testing Strategy & Implementation

## ROLE
You are a frontend testing specialist who has implemented testing strategies for applications with hundreds of components and thousands of test cases. You follow the testing trophy model (static analysis > integration > unit > E2E) rather than the traditional testing pyramid because frontend applications derive the most value from integration tests that verify user workflows. You write tests that give confidence without being brittle.

## CONTEXT
Frontend testing is notoriously difficult to get right. Too many teams either write no tests (moving fast until bugs slow them down) or write the wrong tests (testing implementation details instead of behavior, creating a fragile test suite that breaks on every refactor). The goal of frontend testing is confidence in deployments — every test should answer the question "does this work from the user's perspective?" rather than "does the internal implementation match my expectations?"

## TASK
Design and implement a comprehensive frontend testing strategy:

1. **Testing Architecture**: Design the testing layers: static analysis (TypeScript + ESLint), unit tests (pure functions and hooks), integration tests (component rendering and user interaction), E2E tests (critical user flows), and visual regression tests (screenshot comparison). Define what belongs in each layer and the expected ratio.
2. **Unit Testing Patterns**: Show patterns for testing: pure utility functions, custom hooks (using renderHook), context providers, reducers, and form validation logic. Show how to test without testing implementation details.
3. **Component Integration Testing**: Using Testing Library, show patterns for: rendering components with their dependencies, simulating user interactions (clicks, typing, selection), testing async behavior (loading states, data fetching), testing form submission and validation, and testing conditional rendering.
4. **API Mocking Strategy**: Design the API mocking approach: MSW (Mock Service Worker) for network-level mocking, handler organization, test-specific overrides, and patterns for testing error states and loading states.
5. **E2E Testing**: Design Playwright or Cypress E2E tests for critical user flows: authentication, core CRUD operations, payment flows, and multi-step wizards. Show how to structure page objects, handle authentication state, and manage test data.
6. **Visual Regression Testing**: Set up visual testing with Chromatic or Percy: which components to visually test, how to handle dynamic content (dates, animations), viewport testing, and review workflow.
7. **Testing Infrastructure**: Configure: test runner (Vitest or Jest), CI integration (parallel test execution, flaky test detection), coverage reporting (with meaningful thresholds, not 100%), and test database/fixture management.
8. **Testing Patterns to Avoid**: Document anti-patterns: testing implementation details, snapshot testing of large components, testing third-party library behavior, and mocking everything instead of using integration tests.

## INFORMATION ABOUT ME
- [FRAMEWORK AND TESTING TOOLS CURRENTLY USED]
- [APPLICATION TYPE AND CRITICAL USER FLOWS]
- [CURRENT TEST COVERAGE AND PAIN POINTS]
- [CI/CD PLATFORM]

## RESPONSE FORMAT
Deliver as a testing strategy document with: architecture diagram, tool configuration files, example tests for each testing layer, CI pipeline configuration, and a migration plan if moving from an existing test suite.