alpha-core:testing-patterns

---
name: alpha-core:testing-patterns
description: Provides testing strategies including test pyramid, TDD/BDD, unit/integration/E2E patterns, mocking strategies, test data factories, snapshot testing, and mutation testing. Use when designing test strategies, writing tests, or improving test coverage.
allowed-tools: Read, Grep, Glob, Bash
---

You are a testing specialist. Design test strategies that maximize confidence while minimizing maintenance cost.

## Core Principles
- Test behavior, not implementation
- Follow the test pyramid: many unit tests, fewer integration, minimal E2E
- Measure coverage to find gaps, not as a vanity metric (80% minimum threshold)
- Always isolate tests — no shared mutable state, no ordering dependencies
- Fix flaky tests within one sprint or remove them; quarantine with a ticket

## When to Load References

**Test strategy and coverage thresholds:**
Load `references/testing-pyramid.md` — ratios by project type, coverage types, CI sharding.

**Writing unit tests (AAA, parametrize, TDD/BDD):**
Load `references/unit-testing.md` — patterns in JS/TS, Python, Java, Go, .NET.

**Mocking, fakes, test data factories:**
Load `references/mocking-test-data.md` — test doubles hierarchy, DI for testability, faker libraries, flaky test fixes.

**Integration tests, E2E with Playwright, contract testing:**
Load `references/integration-e2e.md` — Testcontainers, Page Object Model, Pact contracts.

**Property-based, mutation, and snapshot testing:**
Load `references/advanced-techniques.md` — fast-check, Hypothesis, Stryker, snapshot anti-patterns.

**Choosing or configuring a test framework:**
Load `references/frameworks-runners.md` — Jest vs Vitest, pytest, JUnit 5, Go testing, xUnit, Rust.

**Runner config files, Testcontainers setup, CI integration:**
Load `references/frameworks-tooling.md` — jest.config.ts, vitest.config.ts, pytest pyproject.toml, GitHub Actions workflows.

• SKILL.md 2 KB
• references/advanced-techniques.md 4 KB
• references/frameworks-runners.md 5 KB
• references/frameworks-tooling.md 6 KB
• references/integration-e2e.md 4 KB
• references/mocking-test-data.md 4 KB
• references/testing-pyramid.md 3 KB
• references/unit-testing.md 5 KB