Tutorials

Email Testing in Node.js with Jest

The Devmailr TeamJune 23, 20266 min read

When your Node.js app sends a verification email, a Jest or Vitest test should be able to confirm it actually went out — and read the code or link inside. Here’s a small, dependency-free way to do that against a disposable inbox.

The idea

Unlike browser e2e (Playwright/Cypress), here you’re testing your backenddirectly: call your “send verification email” code (or hit your API), then read the email that lands in a disposable inbox and assert on it. Node 18+ has fetch built in, so no client library is needed.

A tiny helper

devmailr.js

const BASE = 'https://api.devmailr.app/api'
const headers = { Authorization: `Bearer ${process.env.DEVMAILR_API_KEY}` }

export async function createInbox(prefix) {
  const res = await fetch(`${BASE}/mailboxes`, {
    method: 'POST',
    headers: { ...headers, 'Content-Type': 'application/json' },
    body: JSON.stringify({ prefix }),
  })
  return res.json()
}

export async function waitForEmail(mailboxId, query = '') {
  const res = await fetch(`${BASE}/mailboxes/${mailboxId}/wait?timeout=60&${query}`, { headers })
  if (res.status === 404) throw new Error('No matching email arrived in time')
  return res.json()
}

export async function deleteInbox(mailboxId) {
  await fetch(`${BASE}/mailboxes/${mailboxId}`, { method: 'DELETE', headers })
}

The test (Jest or Vitest)

Same API in both. Create an inbox, trigger your sender, assert on the email, clean up:

email.test.js

import { createInbox, waitForEmail, deleteInbox } from './devmailr'
import { sendVerificationEmail } from '../src/email' // your app code

let inbox
beforeAll(async () => { inbox = await createInbox(`jest-${Date.now()}`) })
afterAll(async () => { await deleteInbox(inbox._id) })

test('sends a verification email with a 6-digit code', async () => {
  await sendVerificationEmail(inbox.address)

  const email = await waitForEmail(inbox._id, 'has_code=true')

  expect(email.from).toContain('noreply@myapp.com')
  expect(email.subject).toMatch(/verify/i)
  expect(email.extractedCodes[0]).toMatch(/^\d{6}$/)
}, 65_000)

Raise the timeout: /wait can block up to 60s, so bump the per-test timeout above it — the third arg 65_000 in Jest (as above), or { timeout: 65_000 } in Vitest. Otherwise the runner gives up before the email arrives.

Testing a reset link

javascript

test('password reset email contains a working link', async () => {
  await sendPasswordReset(inbox.address)
  const email = await waitForEmail(inbox._id, 'subject=' + encodeURIComponent('reset'))
  const url = new URL(email.primaryLink)
  expect(url.searchParams.get('token')).toBeTruthy()
}, 65_000)