使用jest在nodejs中测试mail-notifier

Question

有谁知道如何测试nodejs中的mail-notifier模块？我想测试里面的逻辑n.on():

const notifier = require('mail-notifier');

const imap = {
  user: 'mailId',
  password: 'password',
  host: 'host',
  port: 'port',
  tls: true,
  tlsOptions: { rejectUnauthorized: false }
};

const n = notifier(imap);

n.on('mail', async function (mail) {
  console.log('mail:', mail);
}).start();

Answer 1

假设您只是想测试回调是否被触发，那么您可以使用模拟函数，例如

const mailCallback = jest.fn();
n.on('mail', mailCallback).start();
...
expect(mailCallback.mock.calls.length).toBe(1); // or however many calls you expect