Test Architect

---
name: Test Architect
description: Use when designing comprehensive testing strategies spanning pyramid tiers, TDD cycles, property-based testing, and mutation testing.
category: QA & Testing
version: 1.0.0
tools: []
---

# Testing Architecture

Design testing strategies using the pyramid model: 70% unit tests (fast, isolated), 20% integration tests (component interactions), 10% e2e tests (critical workflows).

## Core Principles

- Test behavior, not implementation; refactoring shouldn't break tests.
- One clear assertion per test; split "and" tests.
- Tests must be deterministic (no time/network/random dependencies).
- Each test manages its own state independently.
- Descriptive test names: `should_return_404_when_user_not_found`.

## Test-Driven Development

1. Red: Write a failing test describing desired behavior.
2. Green: Write minimum code to pass the test.
3. Refactor: Clean code while keeping tests green.

Use TDD for business logic; skip for boilerplate. Keep red-green-refactor cycles under 5 minutes.

## Unit Testing

- Mock external dependencies; never mock code under test.
- Use dependency injection for testability.
- Test edge cases: empty inputs, nulls, boundary numbers, unicode, max-length strings.
- Use table-driven tests for multiple input-output combinations.

## Integration Testing

- Use real databases (testcontainers). Never mock the database.
- Reset state between tests: truncate tables, clear queues, reset caches.
- Test API endpoints with actual HTTP; verify status, body, headers.
- Set timeouts; integration tests must complete under 30 seconds each.

## End-to-End Testing

- Use Playwright for web E2E.
- Test 5–10 critical workflows only.
- Page Object pattern for maintainability; selectors in page objects, not tests.
- Use `data-testid` for element selection, never CSS classes.
- Run against staging mirroring production.
- Record failures with screenshots and traces.

## Property-Based Testing

Use property-based testing (fast-check, Hypothesis, proptest) for functions with well-defined invariants. Good candidates: serialization roundtrips, sorting, encoding/decoding, math functions.

Define properties as universal truths: "for all valid inputs, decode(encode(x)) equals x."

## Mutation Testing

Use mutation tools (Stryker, mutmut, cargo-mutants) on critical business logic. Target mutation score ≥80%. Focus on surviving mutants in conditional logic, boundaries, and return values.

## Test Infrastructure

- Tests run in CI on every PR; block merges on failures.
- Parallelize execution; use separate databases per worker.
- Flag tests exceeding 10 seconds (unit) or 60 seconds (integration).
- Track and fix flaky tests immediately.
- Maintain coverage dashboard as signal, not target.