如何用Jest测试nodemailer？

Question

我创建了一个小页面，用于将通知发送到邮件。

我正在使用nodejs和nodemailer发送通知。我的代码可以很好地发送通知。

require('dotenv').config();
const express = require('express')
const router = express.Router()
const {Pool,Query} = require('pg')
const path = require('path')
const nodemailer = require('nodemailer');

var config=require('../../config.json') 
nodemailer.createTestAccount((err,account)=>{
        const bodyMsg = `
        <h3>New Contact Request</h3>
           <ul>
               <li>Name: ${req.body.name}</li>
               <li>Email: ${req.body.email}</li>

           </ul>
           <h3>Message</h3>
           <p>${req.body.msg}</p>

        `
        let transporter = nodemailer.createTransport({
         host: config.SMTP.host,
         port: config.SMTP.port,
         secure: false, 
         auth: {
             user: process.env.EMAIL,
             pass: process.env.PASSWORD
         },
         tls:{
           rejectUnauthorized:false
         }
       });

      //  setup email data with unicode symbols
       let mailOptions = {
           from: `"Contact us " ${config.SMTP.email}`, 
           to: process.env.TO, 
           subject: 'New report', 
           text: req.body.msg, 
           html: bodyMsg 
       };

       // send mail with defined transport object
       transporter.sendMail(mailOptions, (error, info) => {
           if (error) {
               return console.log(error);
           }
           console.log('Message sent: %s', info.messageId);   
           console.log('Preview URL: %s', nodemailer.getTestMessageUrl(info));

           //res.render('contact', {msg:'Email has been sent'});
       });
      })
   })


 })

如何使用Jest或酶测试nodemailer？