Mocking email function in nodejs

Question

I've got a mailer function I've built and trying to shore up the coverage. Trying to test parts of it have proven tricky, specifically this mailer.smtpTransport.sendMail ``` var nodemailer = require('nodemailer') var mailer = {} mailer.smtpTransport = nodemailer.createTransport('SMTP', { 'service': 'Gmail', 'auth': { 'XOAuth2': { 'user': 'test@test.com', 'clientId': 'googleClientID', 'clientSecret': 'superSekrit', 'refreshToken': '1/refreshYoSelf' } } }) var mailOptions = { from: 'Some Admin ', } mailer.verify = function(email, hash) { var emailhtml = 'Welcome to TestCo. Click this '+hash+'' var emailtxt = 'Welcome to TestCo. This is your hash: '+hash mailOptions.to = email mailOptions.subject = 'Welcome to TestCo!' mailOptions.html = emailhtml mailOptions.text = emailtxt mailer.smtpTransport.sendMail(mailOptions, function(error, response){ if(error) { console.log(error) } else { console.log('Message sent: '+response.message) } }) } ``` I'm unsu…

Accepted Answer

This example works fine for me

======== myfile.js ========

```
// SOME CODE HERE

transporter.sendMail(mailOptions, (err, info) => {
  // PROCESS RESULT HERE
});
```

======== myfile.spec.js (unit test file) ========

```
const sinon = require('sinon');
const nodemailer = require('nodemailer');
const sandbox = sinon.sandbox.create();

describe('XXX', () => {
  afterEach(function() {
    sandbox.restore();
  });

it('XXX', done => {
    const transport = {
      sendMail: (data, callback) => {
        const err = new Error('some error');
        callback(err, null);
      }
    };
    sandbox.stub(nodemailer, 'createTransport').returns(transport);

// CALL FUNCTION TO TEST

// EXPECT RESULT
  });
});
```

Mocking email function in nodejs

Solution

Problem