JavaScript unit testing with external module

Question

I am working on an existing node project where the code structure for most of the js files looks something like following.

    var mod1 = require("mod1");
    var mod2 = require("mod2");
    var modn = require("moden");


    function func1(data, callback) {
        // Do some validation with data etc.. 
        // Use one or more imported modules here 

    }

    function func2(data, callback) {
        // Do some validation with data etc.. 
        // Use one or more imported modules here 

    }


    exports.func1 = func1
    exports.func2 = func2 

How can unit test func1, while not being dependent on the imported modules? How can I mock/stub them? I come from the Java world so I am familiar with the mocking concepts, but here I am not sure how can I mock the globally declared module imports using require.

Currently we are using nodeunit for the unit testing purpose, but it tests very small part of the code.

I am reading about simon.js and testdouble but not sure how to use them to mock the global variables.

Any help/direction is appreciated.

Answer 1

For overriding dependencies during testing I recommend to use in your situation the https://github.com/thlorenz/proxyquire module

For quick exmple I paste example from project github

foo.js:

var path = require('path');

module.exports.extnameAllCaps = function (file) {
 return path.extname(file).toUpperCase();
};

module.exports.basenameAllCaps = function (file) {
 return path.basename(file).toUpperCase();
}

foo.test.js:

var proxyquire =  require('proxyquire')
, assert     =  require('assert')
, pathStub   =  { };

// when no overrides are specified, path.extname behaves normally
var foo = proxyquire('./foo', { 'path': pathStub });
assert.equal(foo.extnameAllCaps('file.txt'), '.TXT');