Testing Strategy

Overview

Analyze the project context and recommend a comprehensive testing strategy. This skill selects appropriate frameworks, defines the testing pyramid, establishes coverage thresholds, and generates test configuration files. The goal is a repeatable, measurable testing foundation that the team can maintain.

Announce at start: "I'm using the testing-strategy skill to define the testing approach."

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Phase 1: Analyze Project

Goal: Understand the current stack, existing tests, and CI setup before recommending anything.

Actions

1. Identify the tech stack (language, framework, runtime)
2. Survey existing tests (what testing exists already?)
3. Review CI/CD pipeline (how do tests run?)
4. Measure current coverage levels
5. Map external dependencies (services, databases, APIs)

Discovery Commands

# Identify test files
find . -name "*.test.*" -o -name "*.spec.*" | head -30

# Check for test config
ls vitest.config.* jest.config.* pytest.ini pyproject.toml .mocharc.* 2>/dev/null

# Check current coverage
cat coverage/coverage-summary.json 2>/dev/null || echo "No coverage report found"

# Check CI config
cat .github/workflows/*.yml 2>/dev/null | head -50

STOP — Do NOT proceed to Phase 2 until:

• Tech stack is identified
• Existing test infrastructure is mapped
• CI pipeline status is known
• External dependencies are listed

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Phase 2: Recommend Testing Pyramid

Goal: Select frameworks and define the pyramid ratios.

Framework Selection Table

Stack	Unit	Integration	E2E
Node.js/TS	Vitest	Vitest + Supertest	Playwright
React/Next.js	Vitest + Testing Library	Vitest + MSW	Playwright/Cypress
Python	pytest	pytest + httpx	Playwright
Go	testing + testify	testing + testcontainers	Playwright
Rust	cargo test	cargo test + testcontainers	-
PHP/Laravel	Pest/PHPUnit	Pest + HTTP tests	Playwright/Dusk

Testing Pyramid Ratios

        /\
       /  \     E2E Tests (10%)
      /    \    Critical user journeys only
     /------\
    /        \   Integration Tests (30%)
   /          \  API endpoints, DB queries, service interactions
  /------------\
 /              \ Unit Tests (60%)
/                \ Pure functions, business logic, utilities

What to Test at Each Level

Level	Test These	Do NOT Test These
Unit (60%)	Pure functions, business logic, data transformations, validations, state management	Framework internals, third-party libraries
Integration (30%)	API endpoints, database queries, service-to-service calls, auth flows	Individual functions in isolation
E2E (10%)	Critical user journeys (signup, purchase), cross-browser, accessibility	Edge cases (handle at unit level)

STOP — Do NOT proceed to Phase 3 until:

• Framework selection matches the tech stack
• Pyramid ratios are defined
• Testing scope at each level is documented

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Phase 3: Define Coverage Thresholds

Goal: Set realistic, enforceable coverage targets.

Coverage Threshold Table

Category	Minimum	Target	Notes
Overall	70%	85%	Lines covered
Critical paths	90%	95%	Auth, payments, data access
New code (PRs)	80%	90%	Enforced in CI
Utilities	95%	100%	Pure functions are easy to test

Threshold Selection Decision Table

Project Maturity	Overall Minimum	New Code Minimum	Rationale
Greenfield	80%	90%	Start high, maintain standard
Active (good coverage)	70%	85%	Maintain and improve
Legacy (low coverage)	50%	80%	Raise floor gradually
Prototype/MVP	60%	70%	Cover critical paths, accept gaps

STOP — Do NOT proceed to Phase 4 until:

• Coverage thresholds are realistic for the project maturity
• Critical path coverage targets are defined
• CI enforcement strategy is decided

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Phase 4: Generate Configuration

Goal: Produce working test configuration files and CI integration.

Actions

1. Generate test runner config (vitest.config.ts, jest.config.js, pytest.ini)
2. Configure coverage with thresholds
3. Add test commands to CI workflow
4. Set up test environment (.env.test, test databases)

Example: Vitest Config

import { defineConfig } from 'vitest/config';

export default defineConfig({
  test: {
    globals: true,
    environment: 'jsdom',
    coverage: {
      provider: 'v8',
      reporter: ['text', 'json', 'html'],
      thresholds: {
        lines: 80,
        functions: 80,
        branches: 80,
        statements: 80,
      },
    },
    include: ['src/**/*.test.{ts,tsx}'],
  },
});

STOP — Do NOT proceed to Phase 5 until:

• Config files are syntactically valid
• Coverage thresholds match Phase 3 decisions
• CI integration commands are defined

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Phase 5: Create Test Templates

Goal: Provide example test files demonstrating project conventions.

Actions

1. Create a unit test example with Arrange-Act-Assert
2. Create an integration test with setup/teardown
3. Create mock/stub patterns for external dependencies
4. Create test data factories/fixtures
5. Create a snapshot test example (when appropriate)

STOP — Verification Gate before claiming complete:

• Framework selection matches tech stack
• Coverage thresholds are realistic
• Test configuration files are valid
• Example tests actually run
• CI integration is configured

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Anti-Patterns / Common Mistakes

Anti-Pattern	Why It Is Wrong	Correct Approach
Testing implementation details	Breaks on every refactor, provides false confidence	Test behavior and outcomes
Excessive mocking	Tests nothing real, mocks mask real failures	Mock at boundaries only
Brittle CSS selectors in E2E	Break with styling changes	Use data-testid or accessible roles
Test interdependence	Ordering failures, flaky in CI	Each test must run independently
Slow tests blocking CI	Developers skip running tests	Parallelize, use test databases, mock external APIs
Snapshot overuse	Snapshots approved without reading, stale baselines	Use for stable output only
No coverage enforcement in CI	Coverage degrades over time	Enforce thresholds in CI pipeline
Same coverage target everywhere	Utilities and critical paths differ	Use per-category thresholds

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Decision Table: Mock Strategy

Dependency Type	Mock Strategy	Example
External API	MSW / nock / responses	Third-party payment API
Database	Test database or in-memory	PostgreSQL test container
File system	Virtual FS or temp directory	File upload processing
Time/Date	Fake timers	Expiration logic
Environment vars	Override in test setup	Feature flags
Random/UUID	Seed or stub	ID generation

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Integration Points

Skill	Relationship
test-driven-development	Strategy defines frameworks; TDD defines the cycle
acceptance-testing	Strategy includes acceptance test infrastructure
code-review	Review checks that tests follow the defined strategy
senior-frontend	Frontend testing uses strategy-selected frameworks
senior-backend	Backend testing uses strategy-selected frameworks
performance-optimization	Load tests are part of the overall testing strategy
webapp-testing	Playwright E2E tests follow strategy pyramid

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Key Principles

• Test behavior, not implementation — what it does, not how
• Fast feedback — unit tests should run in seconds
• Deterministic — no flaky tests, no time-dependent logic
• Readable — tests are documentation; make them clear
• Maintainable — tests should help refactoring, not block it

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Skill Type

FLEXIBLE — Adapt framework selection and coverage thresholds to the project context. The five-phase process and testing pyramid structure are strongly recommended but can be scaled to project size.