agents: Skill for Claude Code

Testing Engineer

Expert in writing production-quality tests. Focused on Vitest, Playwright, pytest, and Go testing.

Test Strategy

E2E (Playwright)         → Critical user flows (login, checkout, signup)
Integration (Vitest)     → API endpoints, service layer, DB queries
Unit (Vitest)            → Business logic, utilities, validation, transformations

TypeScript / Vitest

Setup

// vitest.config.ts
import { defineConfig } from 'vitest/config'

export default defineConfig({
  test: {
    environment: 'node',        // for API tests
    // environment: 'jsdom',    // for React component tests
    setupFiles: ['./src/test/setup.ts'],
    coverage: {
      provider: 'v8',
      reporter: ['text', 'html'],
      exclude: ['**/node_modules/**', '**/test/**'],
    },
  },
})

Unit Test Template

import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest'
import { UserService } from './user.service'
import { prismaMock } from '@/test/mocks/prisma'

describe('UserService', () => {
  let service: UserService

  beforeEach(() => {
    service = new UserService(prismaMock)
  })

  afterEach(() => {
    vi.clearAllMocks()
  })

  describe('createUser', () => {
    it('should hash password before saving', async () => {
      // Arrange
      const input = { email: '[email protected]', password: 'plain123' }
      prismaMock.user.create.mockResolvedValue({
        id: '1',
        email: input.email,
        password: 'hashed',
        createdAt: new Date(),
      })

      // Act
      const result = await service.createUser(input)

      // Assert
      expect(prismaMock.user.create).toHaveBeenCalledWith({
        data: expect.objectContaining({
          email: input.email,
          password: expect.not.stringContaining('plain123'),
        }),
      })
    })

    it('should throw ConflictError when email exists', async () => {
      prismaMock.user.create.mockRejectedValue(
        new Prisma.PrismaClientKnownRequestError('', { code: 'P2002', clientVersion: '' })
      )

      await expect(service.createUser(input)).rejects.toThrow(ConflictError)
    })
  })
})