📩 jest-smtp

This jest extension module provides an ad-hoc SMTP server, as well as custom jest matchers, in order to test email sendings. This is meant to use in end-to-end webserver tests.

It leverages Nodemailer's smtp-server and mailparser modules.

Installation

Add to your project

npm i -D jest-smtp

Add to jest config

In the jest section of your package.json file:

"jest": {
    ...,
    "setupFilesAfterEnv": [
      "jest-smtp",
      "<rootDir>/tests/jest-setup.ts"
      ...
    ],
}

Using it

Globally

You can add jest-smtp globally to your jest-setup file.

import { createJestSMTPServer } from 'jest-smtp';


beforeAll(() => {
    global.smtpServer = createJestSMTPServer();
});

afterAll(() => {
    global.smtpServer.close();
});

beforeEach(() => {
    global.smtpServer.resetMails();
});

If you use typescript you should add this declaration in your jest.d.ts file:

declare namespace NodeJS {
  export interface Global {
    smtpServer: import('jest-smtp').JestSMTPServer;
  }
}

In a test

import { createJestSMTPServer } from 'jest-smtp';

describe('test my server', () => {
    const smtpServer = createJestSMTPServer();

    afterAll(() => {
        smtpServer.close();
    });

    beforeEach(() => {
        smtpServer.resetMails();
    });
})

Documentation

Jest matchers

jest-smtp provides custom matchers

toHaveReceivedEmails

This tests the number of mails received by the server.

expect(smtpServer).toHaveReceivedEmails(1);

toHaveReceivedEmailMatching

This tests if an email matching the provided fields was sent. This is useful so you don't have to provide an exact match but only test the relevant fields.

The fields are structured by mailparser, you can find the reference here: https://nodemailer.com/extras/mailparser/#mail-object

Be especially aware that the to, from, cc etc... fields are structured as objects, not strings.

expect(smtpServer).toHaveReceivedEmailMatching({
    subject: 'My e-mail subject',
    from: {
        name: 'Don\'t reply',
        address: 'noreply@myapp.com'
    }
});

createJestSMTPServer

jest-smtp only exports one function :

const { emails, server, close, resetMails } = createJestSMTPServer({
    port: 465,
    host: undefined,
    options: ()
})

Parameters

port: the port the server will be listening on. Default is 465.

host: the host the server will be listening on (pretty unuseful is you ask me)

options: these options will be passed to the smtp-server instance constructor. See here for reference: https://nodemailer.com/extras/smtp-server/#usage

The default options provided are :

{
  authMethods: ["PLAIN", "LOGIN"],
  authOptional: true,
  onData: ... // if you override this function it will break the main features of the plugin
};

returned objects

• resetEmails

convenience method to reset the list of received emails between the tests.

• close

shortcut to server.close method. This must be called after all tests or jest will timeout.

• emails

The list of ParsedMail objects received. You can access it to do extra tests on the content of the emails.

• server

The smtp-server instance.