aws-stubbing.js

const simple = require('simple-mock');
const AWS = require('aws-sdk');

const S3 = (new AWS.S3()).constructor.prototype;
describe('store', () => {
  beforeEach(() => {
    simple.mock(S3, 'getObject').callbackWith(null, mockResult);
  });
  afterEach(() => {
    simple.restore();
  });
  // ...
});