How to simulate an object created with require

Question

I am new to node.js, and in most of the codes I have seen, I do not see inline constructor IoC / DI constructors.

Instead, the node.js require () extension is usually required to create local vars that allow the export of external modules.

But when writing unit tests (which isolate a single layer / function), how do you mock the modules available through the vars you created?

/helpers/dataHelper.js

var dataModel = require('../models/dataModel.js');

var getFormattedDataForRegion = function(region, callback) {
    var data = {};
    // validate region
    // query dataModel
    // async.map format data items
    // callback(data);
}

/tests/dataHelperTests.js

describe('dataHelper', function(){

    it('getFormattedDataForRegion returns expected response', function(done){

        var expectedData = {};
        // populate expectedData

        // **** need some way to mock dataModel *****

        dataHelper.getFormattedDataForRegion("west", function(data){
            expect(data).to.eql(expectedData);
            done();
        });
    });

Answer 1

This is done using proxyquire .

, , "node" . :

var proxyquire =  require('proxyquire'),
    dataModelMock = require('./mocks/dataModel');

proxyquire('path/to/helpers/dataHelper.js', { '../models/dataModel.js': dataModelMock });