Tdd Workflow

Step 2 — Write Failing Test (RED)

Write a test that describes the expected behavior. It must fail for the right reason — missing implementation, not a broken test setup.

import { describe, it, expect } from 'vitest'
import { createUser } from './userService'

describe('createUser', () => {
  it('returns the created user with hashed password', async () => {
    const result = await createUser({ email: '[email protected]', password: 'secret' })
    expect(result.email).toBe('[email protected]')
    expect(result.password).not.toBe('secret') // should be hashed
  })

  it('throws when email already exists', async () => {
    await createUser({ email: '[email protected]', password: 'secret' })
    await expect(createUser({ email: '[email protected]', password: 'other' }))
      .rejects.toThrow('Email already in use')
  })
})

Run and verify failure:

pnpm test -- --reporter=verbose createUser

RED gate: the test must compile, execute, and fail for the intended reason. A test that was only written but not run does not count as RED.

Git checkpoint: