TypeError: sns.publish is not a function , jest mock AWS SNS

Question

I am trying to mock AWS.SNS and I am getting error. I referred posts on StackOverflow and could come up with below. Still, I am getting an error. I have omitted the irrelevant p

Answer 1

Here is the unit test solution:

index.ts:

import { SNS } from 'aws-sdk';

export const thishandler = async (event): Promise<any> => {
  const snsMessagetoBeSent = {};
  const response = await sendThisToSNS(snsMessagetoBeSent);
  return response;
};

async function sendThisToSNS(thisMessage) {
  const sns = new SNS();
  const TOPIC_ARN = process.env.THIS_TOPIC_ARN;

  const params = {
    Message: JSON.stringify(thisMessage),
    TopicArn: TOPIC_ARN,
  };

  return await sns.publish(params).promise();
}

index.test.ts:

import { thishandler } from './';
import { SNS } from 'aws-sdk';

jest.mock('aws-sdk', () => {
  const mSNS = {
    publish: jest.fn().mockReturnThis(),
    promise: jest.fn(),
  };
  return { SNS: jest.fn(() => mSNS) };
});

describe('59810802', () => {
  let sns;
  beforeEach(() => {
    sns = new SNS();
  });
  afterEach(() => {
    jest.clearAllMocks();
  });
  it('should pass', async () => {
    const THIS_TOPIC_ARN = process.env.THIS_TOPIC_ARN;
    process.env.THIS_TOPIC_ARN = 'OUR-SNS-TOPIC';

    const mockedResponseData = {
      Success: 'OK',
    };
    sns.publish().promise.mockResolvedValueOnce(mockedResponseData);
    const mEvent = {};
    const actual = await thishandler(mEvent);
    expect(actual).toEqual(mockedResponseData);
    expect(sns.publish).toBeCalledWith({ Message: JSON.stringify({}), TopicArn: 'OUR-SNS-TOPIC' });
    expect(sns.publish().promise).toBeCalledTimes(1);
    process.env.THIS_TOPIC_ARN = THIS_TOPIC_ARN;
  });
});

Unit test results with 100% coverage:

 PASS  src/stackoverflow/59810802/index.test.ts (13.435s)
  59810802
    ✓ should pass (9ms)

----------|----------|----------|----------|----------|-------------------|
File      |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
----------|----------|----------|----------|----------|-------------------|
All files |      100 |      100 |      100 |      100 |                   |
 index.ts |      100 |      100 |      100 |      100 |                   |
----------|----------|----------|----------|----------|-------------------|
Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        15.446s

Source code: https://github.com/mrdulin/jest-codelab/tree/master/src/stackoverflow/59810802