Bun test fixtures + InboxTap

Use InboxTap's Bun adapter to start one local SMTP capture server for the test file while every test creates its own inbox. Both listeners use dynamic ports, and the fixture closes them after the file finishes.

Prerequisites

• Bun 1.3 or later

Setup

npm install

Run the tests

bun test

The tests start InboxTap automatically. No separate CLI process or fixed ports are required.

How it works

import { expect, test } from "bun:test";
import { setupInboxTap } from "inboxtap/fixtures/bun";

const inboxTap = setupInboxTap();

test("captures an email", async () => {
  const inbox = await inboxTap.createInbox();
  await inboxTap.transport.sendMail({
    from: "app@local.test",
    to: inbox.address,
    subject: "Welcome",
    text: "Your account is ready.",
  });

  const message = await inbox.waitForMessage({ subject: "Welcome" });
  expect(message.envelope.to).toEqual([inbox.address]);
});

setupInboxTap() registers Bun's asynchronous beforeAll and afterAll hooks. Its preconfigured Nodemailer transport targets the dynamically selected SMTP port and is verified before the tests begin.

Isolation and cleanup

Call createInbox() inside every test. Each call generates a unique recipient, so tests can share the server without sharing messages. The registered teardown closes the transport and both InboxTap listeners even when a test fails.

Troubleshooting

• InboxTap is available only after beforeAll — declare setupInboxTap() at module scope, but call its methods from a test or a later lifecycle hook.
• A wait timed out — confirm the message was sent to that test's inbox.address.
• The process stays open — avoid creating a second transport or server outside the managed fixture unless you also close it.