Mocking AWS SES with Jest

Question

I am trying to mock AWS SES in Jest but continue to get this timeout error:

Timeout - Async callback was not invoked within the 5000ms timeout specified by jest.setTimeout.Timeout - Async callback was not invoked within the 5000ms timeout specified by jest.setTimeout.Error:

I've stripped out the code that is unrelated and verified to be working. Here is the code that uses SES:

import SES from 'aws-sdk/clients/ses';

try {
    /** Initialize SES Class */
    const ses = new SES({ apiVersion: '2010-12-01' });

    await ses.sendTemplatedEmail(sesEmailParams).promise();
} catch(err) {
    return next(internalErrorMessage);
}

Here is the test that uses SES:

import AWS from 'aws-sdk';

test('Should error when ses.sendTemplatedEmail.promise() fails', async (done) => {
    const fakeSesPromise = {
      promise: jest
        .fn()
        .mockImplementationOnce(() => Promise.reject(new Error('This is an SES error'))),
    };

    const fakeSes = {
      sendTemplatedEmail: () => {
        return fakeSesPromise;
      },
    };

    AWS.SES = jest.fn(() => fakeSes);

    await user.forgotPassword(mockRequest, mockResponse, mockNext);

    expect(fakeSesPromise).toHaveBeenCalledTimes(1);
    expect(mockNext).toHaveBeenCalledWith(internalErrorMessage);

    done();
});

I've tried a few other suggested ways which ended with the same result. I am assuming that it has something to do with how the aws-sdk uses the .promise() function.

Any help would be much appreciated!

Update #1:

The below solution from @slideshowp2 works, but will throw this Typescript error:

Property 'mockRejectedValueOnce' does not exist on type '() => Promise<PromiseResult<SendTemplatedEmailResponse, AWSError>>'

for this line:

mockSes.sendTemplatedEmail().promise.mockRejectedValueOnce(new Error('This is an SES error'));

To make it work, just change this line:

const mockSes = new mockSES();

to:

const mockSes = (new SES() as unknown) as { sendTemplatedEmail: jest.Mock; promise: jest.Mock };

Answer 1

Here is a unit test solution using jest.mock(moduleName, factory, options), mock aws-sdk/clients/ses module, SES class and its methods.

E.g.

user.js:

import SES from 'aws-sdk/clients/ses';

const internalErrorMessage = 'internalErrorMessage';

export const user = {
  async forgotPassword(req, res, next) {
    const sesEmailParams = {
      Source: 'Sender Name <sender@recipient.com>',
      Destination: {
        ToAddresses: [],
      },
      Template: 'tpl',
      TemplateData: 'data',
    };
    try {
      const ses = new SES({ apiVersion: '2010-12-01' });
      await ses.sendTemplatedEmail(sesEmailParams).promise();
    } catch (err) {
      return next(internalErrorMessage);
    }
  },
};

user.test.js:

import MockSES from 'aws-sdk/clients/ses';
import { user } from './user';

jest.mock('aws-sdk/clients/ses', () => {
  const mSES = {
    sendTemplatedEmail: jest.fn().mockReturnThis(),
    promise: jest.fn(),
  };
  return jest.fn(() => mSES);
});

describe('61491519', () => {
  test('Should error when ses.sendTemplatedEmail.promise() fails', async () => {
    const mSes = new MockSES();
    const mError = new Error('This is an SES error');
    mSes.sendTemplatedEmail().promise.mockRejectedValueOnce(mError);
    const mockRequest = {};
    const mockResponse = {};
    const mockNext = jest.fn();
    await user.forgotPassword(mockRequest, mockResponse, mockNext);

    expect(MockSES).toBeCalledWith({ apiVersion: '2010-12-01' });
    expect(mSes.sendTemplatedEmail).toBeCalledWith({
      Source: 'Sender Name <sender@recipient.com>',
      Destination: {
        ToAddresses: [],
      },
      Template: 'tpl',
      TemplateData: 'data',
    });
    expect(mSes.sendTemplatedEmail().promise).toBeCalledTimes(1);
    expect(mockNext).toHaveBeenCalledWith('internalErrorMessage');
  });
});

unit test results with 100% coverage:

 PASS  stackoverflow/61491519/user.test.js (10.071s)
  61491519
    ✓ Should error when ses.sendTemplatedEmail.promise() fails (6ms)

----------|---------|----------|---------|---------|-------------------
File      | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
----------|---------|----------|---------|---------|-------------------
All files |     100 |      100 |     100 |     100 |                   
 user.js  |     100 |      100 |     100 |     100 |                   
----------|---------|----------|---------|---------|-------------------
Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        12.115s