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Unit Testing Challenges with Modular JavaScript Patterns
First let us understand what unit testing is and how it helps us. One of the numerous varieties of automated testing is unit testing. Unit tests completely isolate and test relatively small portions of the application, comparing the results to the intended results. When unit testing your application, you normally don't link it to external dependencies like databases, the filesystem, or HTTP services. This is referred to as "full isolation." Since they won't fail as a result of issues with all those external services, unit tests can be quicker and more reliable as a result.
Individual software units, such as groups of computer programme modules, usage scenarios, and operational procedures, are examined to see if they are fit for use using the software testing technique known as unit testing. It is a testing strategy whereby the developer examines each individual module to see whether there is a problem. It has a relationship with how well-functioning the independent modules are.
Keeping the units of code for a project cleanly segregated and organised is usually made easier by modules, which are a crucial component of the architecture of any robust application.
Modules for JavaScript are alternatively called "ES modules" or "ECMAScript modules. The most popular design pattern is JavaScript Modules. It serves to maintain the independence of individual pieces of code from other parts. To support well-structured code, this offers a loose coupling.
In terms of object-oriented languages, modules are simply JavaScript classes. Encapsulation, which prevents access to states and behaviours from other classes, is one of the numerous benefits of classes that was highlighted in a previous piece. The levels of public and private access are created using the module pattern.
Modules must support private scopes by being IIFE (immediately invoked function expression) that serves as a closure to safeguard methods and variables.
Here is the basic example, this is how it looks like.
(function() {
// declare private variables and/or functions
return {
// declare public variables and/or functions
}
})();
Prior to returning the object we intend to return, we create the private variables and/or functions in this case. As these private variables do not belong to the same scope as our closure, code outside of it cannot access them.
Example
In this example let us understand how to implement this in a more specific manner.
<!DOCTYPE html>
<html>
<title>Unit Testing Challenges with Modular JavaScript Patterns - TutorialsPoint</title>
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" countent="IE=edge">
<meta name="viewport" countent="width=device-width, initial-scale=1.0">
</head>
<body>
<div id="result"></div>
<script>
function Football(type) {
this.type = type;
this.country = "italian";
this.getInfo = getFootballInfo;
}
function getFootballInfo() {
return this.country + ' ' + this.type + ' is italian';
}
let italian = new Football('language');
italian.country = "players";
document.getElementById("result").innerHTML = (italian.getInfo());
</script>
</body>
</html>
Revealing Module Pattern
RMP, or the Revealing Module Paradigm, is a well-liked design pattern for Javascript. The concept behind this is that it hides implementation details within a closure and "reveals" only those functions that are meant to be made public through an object literal delivered from the contained function. The pattern was created by Christian Heilmann, and Addy Osmani describes it in his book Learning Javascript Design Patterns. It would seem that the RMP pattern would work well for the testing phase because it offers a public API.
Example 1
The Revealing Module Pattern is a variant of the module pattern. Encapsulation is kept in place while a few variables and methods returned by an object literal are made visible. Let us understand with an example shown below.
<!DOCTYPE html>
<html>
<title>Unit Testing Challenges with Modular JavaScript Patterns - TutorialsPoint</title>
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" countent="IE=edge">
<meta name="viewport" countent="width=device-width, initial-scale=1.0">
</head>
<body>
<div id="resul1"></div>
<div id="resul2"></div>
<script>
let organicFarm = (function() {
let privateVariable = 10;
let privateFarmingMethod = function() {
document.getElementById("resul1").innerHTML = ('These fruits are inside a private farming method!');
privateVariable++;
}
let organicFarmMethod = function() {
document.getElementById("resul2").innerHTML = ('These fruits are from organic farming method!' + '<br>');
}
let otherMethodIWantToFarm = function() {
privateFarmingMethod();
}
return {
first: organicFarmMethod,
second: otherMethodIWantToFarm
};
})();
organicFarm.first(); // Output: These fruits are from oganic farming method!
organicFarm.second(); // Output: These fruits are inside a private farming method!
organicFarm.organicFarmMethod; // undefined
</script>
</body>
</html>
Example 2
This is another example of Revealing Module Pattern in JavaScript
<!DOCTYPE html>
<html>
<title>Unit Testing Challenges with Modular JavaScript Patterns - TutorialsPoint</title>
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" countent="IE=edge">
<meta name="viewport" countent="width=device-width, initial-scale=1.0">
</head>
<body>
<div id="result"></div>
<script>
let farmModule = (function() {
function fruits() {
return 'These fruits are from my farm Module';
}
function vegetables() {
return 'These vegetables are from organic farming';
}
return {
fruits: fruits,
vegetables: vegetables
};
}());
document.getElementById("result").innerHTML = (farmModule.fruits()); // These fruits are from my farm Module
</script>
</body>
</html>
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