Q-Unit : Test your private code

A tested and well-documented code is what we all strive for.

At naukri.com Q-Unit (JavaScript testing framework) has been the integral part of the Front End Development (FED) team since last one year.

Qunit is cool but when it comes “Testing JavaScript’s private functions without modifying the code” it gets rigid.

Let us see step-by-step how we solved the above problem:

Design plugins in object literal format

In object literal format every function is global. Though it makes testing easy but it exposes all our functions which is a paltry way of coding.

Example.

API = {

private : function(){}, //no more private

public : function(){}

}

Keeping separate copy for testing

For better API design we used modular pattern but it is all private with selective public methods. To test various private module we maintained two version of the same file:

Development version
Testing version

Required private functions are made public in the testing version. But this time keeping two files in synch was a major challenge.

Development version

Testing Version

API = (function(){

var private = function(){}

var public = function(){}

return {public:public}

}())

API = (function(){

var private = function(){}

var public = function(){}

return {public:public,

private:private}

}())

Solution to the problem

A global testObject is defined in the actual testing environment. Every private function is defined as a property of this global testObject. If the testObject is available to the code it is used otherwise a new local object is made to hold all the functions.

Normal environment

Testing Environment

API = (function(){

var t = typeof testObject != “undefined” ?testObject : {};

var private = function(){}

var public = function(){}

return {public:public}

}());

var testObject = {};

API = (function(){

var t = typeof testObject != “undefined” ?testObject : {};

t.private = function(){}

t.public = function(){}

return {public:public,

private:private}

}());

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Development version	Testing Version
API = (function(){ var private = function(){} var public = function(){} return {public:public} }())	API = (function(){ var private = function(){} var public = function(){} return {public:public, private:private} }())

Normal environment	Testing Environment
API = (function(){ var t = typeof testObject != “undefined” ?testObject : {}; var private = function(){} var public = function(){} return {public:public} }());	var testObject = {}; API = (function(){ var t = typeof testObject != “undefined” ?testObject : {}; t.private = function(){} t.public = function(){} return {public:public, private:private} }());