describe('TestModule', function() {
  beforeEach('setup sandbox', function() {
    this.sandbox = sinon.sandbox.create();
    this.sandbox.stub(request, 'get');
  });
  ...
  afterEach('restore sandbox' function() {
    this.sandbox.restore();
  });
})


//Other example 

const ApiClient = require('./ApiClient');
const request = require('request');
const sinon = require('sinon');
const chai = require('chai');
const sinonChai = require('sinon-chai');
// Allows us to use expect syntax with sinon
chai.use(sinonChai);
const expect = chai.expect;

describe('ApiClient#get', function() {
  beforeEach('create ApiClient instance', function() {
    this.sandbox = sinon.sandbox.create();
    this.sandbox.stub(request, 'get')
    this.apiClient = new ApiClient(request, 'api-key');
  });
  afterEach('restore stub', function() {
    this.sandbox.restore();
  }
  it('yields the request error if the request fails', function(done) {     
    let requestError = {some: 'error'}
    // Respond with a node-style callback error  
    request.get.yields(requestError); 

    this.apiClient.get('/posts', (err, response) => {
      // Ensure the function was called with expected parameters
      expect(request.get).to.have.been.calledWith('/posts', {apiKey: 'api-key'});
      // Check that the error is the same object that was yielded.
      expect(err).to.equal(requestError);
      return done();
  });
  it('yields INTERNAL_SERVER_ERROR when the response status is 500', function(done) { 
    // Respond with a 500 to simulate a server error
    request.get.yields(null, {status: 500}); 
    
    this.apiClient.get('/posts', (err, response) => {
      // Ensure the function was called with expected parameters
      expect(request.get).to.have.been.calledWith('/posts', {apiKey: 'api-key'});
      // Check that the error is the right string.
      expect(err).to.equal('INTERNAL_SERVER_ERROR');
      return done();
  });
  it('yields an AUTH_ERROR when the response status is 403', function(done) {     
    request.get.yields(null, {status: 403}); // Respond with a 403
    
    this.apiClient.get('/posts', (err, response) => {
      // Ensure the function was called with expected parameters
      expect(request.get).to.have.been.calledWith('/posts', {apiKey: 'api-key'});
      // Check that the error is the right string.
      expect(err).to.have.property('message', 'AUTH_ERROR')
      // Test for publicly visible side effects
      expect(this.apiClient.isApiKeyValid).to.equal(false);
      return done();
  });
});