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

Answer 1

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
  });
});