javascript - Mock code in another module -

i want mock amazon aws s3 getobject

the code want test following one: in helper.js

var aws = require('aws-sdk'); var s3 = new aws.s3();  exports.get_data_and_callback = function(callback, extra){   s3.getobject( {bucket: src_bucket, key: src_key},     function (err, data) {       if (err != null) {         console.log("couldn't retrieve object: " + err);       }else{         console.log("loaded " + data.contentlength + " bytes");          callback(data, extra);       }   }); } 

in test/helper_test.js i wrote test should mock module aws

var assert = require('assert'); var mockery = require('mockery');  describe("helper", function() {    it('loads , returns data s3 callback', function(){     mockery.enable();      var fakeaws = {       s3: function(){           return {             getobject: function(params, callback){             callback(null, "hello")           }         }       }     }     mockery.registersubstitute('aws-sdk', fakeaws);      function replace_function(err, data){       console.log(data);     }      require('../helper.js').get_data_and_callback(replace_function, null);    }); }); 

when require aws in test-file test/helper_test.js this:

aws = require('aws-sdk'); s3 = new aws.s3; s3.getobject(replace_function) 

then code works, prints out hello.

but execution of require('../helper.js').get_data_and_callback(replace_function, null);

doesn't work expected, aws stays same not replaced fakeaws. wrong? maybe have other solutions replace s3 thanks

we have created aws-sdk-mock npm module mocks out aws sdk services , methods. https://github.com/dwyl/aws-sdk-mock

it's easy use. call aws.mock service, method , stub function.

aws.mock('s3', 'getobject', function(params, callback) {     callback(null, 'success'); }); 

then restore methods after tests calling:

aws.restore('s3', 'getobject'); 

this works every service , method in as-sdk.