how to properly stub/mock AWS SecretManager with Jest and TypeScript

Question

I am trying to unit test aws-sdk SecretsManager with Jest and running into some issues, I have a simple caching client

import { SecretsManager } from 'aws-sdk';
import { SecretsManagerIntegrationError } from '../errors';
const cache = new Map();

interface SecretsManagerConfig {
  region?: string;
}

export class SecretsManagerClient {
  secretsManager: SecretsManager;

  constructor(config: SecretsManagerConfig) {
    this.secretsManager = new SecretsManager(config);
  }

  async getSecretFromSecretsManager(secretName: string) {
    try {
      const params = { SecretId: secretName };
      const data = await this.secretsManager.getSecretValue(params).promise();

      if (data.SecretString) {
        return JSON.parse(data.SecretString);
      } else {
        return Buffer.from(data.SecretBinary as any, 'base64').toString('ascii');
      }
    } catch (error) {
      throw new SecretsManagerIntegrationError(`Error retrieving secrets: ${error}`);
    }
  }

  async getSecret(secretName: string) {
    if (!cache.get(secretName)) {
      const secret = await this.getSecretFromSecretsManager(secretName);
      cache.set(secretName, secret);
      return secret;
    }

    return cache.get(secretName);
  }
}

in my test file I have mocked the sdk as so.. seems verbose and something sinon handles pretty straight forward, this assertion fails and I am not sure why..

import { SecretsManagerClient } from '../../src/clients/secretsManagerClient';

jest.mock('aws-sdk', () => {
  return {
    SecretsManager: jest.fn(() => ({
      getSecretValue: jest.fn(() => ({
        promise: jest.fn(() => ({
          SecretString: JSON.stringify('cool-secrets-here'),
        })),
      })),
    })),
  };
});

describe('SecretsManagerClient', () => {
  let secretsManager: SecretsManagerClient;

  beforeEach(() => {
    secretsManager = new SecretsManagerClient({});
  });

  describe('when a cached value does not exist', () => {
    it('queries the secretsManager', async () => {
      const getSecretFromSecretsManager = jest.spyOn(secretsManager, 'getSecretFromSecretsManager');

      await secretsManager.getSecret('cool-secret');

      expect(getSecretFromSecretsManager).toHaveBeenCalledTimes(1);
    });
  });

  
  describe('when a cached value exists', () => {
    it('uses the cached value', async () => {
      const getSecretFromSecretsManager = jest.spyOn(secretsManager, 'getSecretFromSecretsManager');

      await secretsManager.getSecret('cool-secret');
      await secretsManager.getSecret('cool-secret');

      expect(getSecretFromSecretsManager).toHaveBeenCalledTimes(1);
    });
  });
});

user_13494542 · Answer

I have achieved this mocking of AWS service using sinon stubs. There is an example of the code as below.

import AWS from 'aws-sdk'
import sinon from 'sinon'

let sinonSandbox

const beforeEach = (done) => {
   sinonSandbox = sinon.sandbox.create()
   done()
}

const afterEach = done => {
   sinonSandbox.restore()
   done()
} 
lab.test('test name', (done) => {
    sinonSandbox.stub(AWS, 'SecretsManager')
      .returns({
        getSecretValue: () => {
          return {
            SecretValue: 'Secret-Value'
          }
        }
    })
    done()
})

You can also create an aws-sdk-mock npm module which mocks out all the AWS SDK services and methods.

It's really easy to use. Just call AWS.mock with the service, method and a stub function.

AWS.mock('SecretsManager', 'getSecretValue', function(params, callback) {
    callback(null, 'success');
});

Then restore the methods after your tests by calling:

AWS.restore('SecretsManager', 'getSecretValue');

Sinon Links:

Sinon Stub Latest Version

stub-promise-aws-sdk-node-js

aws-sdk-mock Links:

aws-sdk-mock

https://www.npmjs.com/package/aws-sdk-mock

how to properly stub/mock AWS SecretManager with Jest and TypeScript

1 Answers