Optimizing The Performance of Web Applications With Jest
Tags: performance, jest, webdev, node
Published: 2024-02-21 15:43:33

Performance testing is an encompassing yet underrated field of software development and it’s a must-have skill as a software developer to prevent common software failure issues that occur among production applications. It is a routine software practice which is carried out to determine the stability of a system in terms of scalability, reliability and data management amongst other parameters. 

In this tutorial, I hope to walk you through Performance testing, what it entails, and the common tools used for backend testing and also, do a demo performance testing project together. The tutorial is simplified and suitable for beginners, mid developers and professional developers. Extensive knowledge of this skill is fundamental to growing as a backend developer and can serve as a revision for expert developers. With all said, let's dive in.

Right now, I would shortly highlight the necessary prerequisites needed to fully harness all that would be discussed in this tutorial.  
•	Intermediate Knowledge of Node JS
•	Basic knowledge of JavaScript operation
•	Knowledge of API development


## What is Performance testing all about?
It serves quite a lot of purposes among which is to test for system efficiency in performing and sustaining tasks. It also serves as a standard to compare systems of varying efficiency and build and also suggests the most effective among them all.

It also helps to reveal vulnerabilities. State-of-the-art testing tools are well optimized to efficiently analyze the code lines to detect any error and are quick to highlight the areas where these occur.  

 The end goal of performance testing is dependent on the use of the application in question. The end goal can either be concurrency-oriented or transaction rate oriented depending on whether the app involves end users or not. 
Performance testing could entail Load testing, which is usually carried out to evaluate the behavior of a web service under a specific expected load.  Other types of testing that can be assessed include Integration testing, spike testing, soak testing and stress testing. 




## Examples of performance testing tools

There are quite a lot of tools which are commonly used in our contemporary times to test the efficacy and latency of web applications. In this section, we hope to discuss on some of the tools used, and highlight their strengths and use cases. 

[_Jest_](https://www.npmjs.com/package/jest): This is a multi-platform testing tool used to assess the correctness of JavaScript-based applications. It was initially created to test the efficiency of React applications but has since been extended to assess the efficiency of Node Js apps. It also offers a code coverage feature. 

[_Mocha_](https://www.npmjs.com/package/mocha): Mocha is a concise asynchronous JavaScript-based testing tool for node Js applications. It is also used with assertion libraries such as Chai and should. 

[_Pythagora_](https://github.com/Pythagora-io/pythagora): This tool offers a unique integrating testing feature to help test how different part of the application works together. It also has the code coverage feature.

[_Artillery_](https://artillery.io): This is a stack agnostic testing tool i.e. it can be used for multiple web applications based on different programming languages and still produce an optimal test outcome. This tool provides efficient Load testing features which help to determine the optimal status of the application when exposed to a large load of traffic. It also checks the speed at which an app responds to a user request without crashing. 
[_Ava_](https://www.npmjs.com/package/ava): Ava is a JavaScript-based performance unit testing tool used to test the efficacy of Node JS applications. It works asynchronously running multiple concurrent tests to determine the suitability of multiple code units. 

[_Loadtest_](https://www.npmjs.com/package/loadtest): This is a special Node package which is used to load test ``Node JS`` applications to evaluate the ability of the application to cope with requests of varying amount and to evaluate for efficiency and concurrency.

[_Apache J-meter_](https://jmeter.apache.org): Apache JMeter offers load-testing features for web applications. It has an in-built IDE to enable interaction with the user. It is multithreaded increasing its ability to mimic several users. 

There are other testing tools which are also equally useful. However, in this tutorial, we will be utilizing ``Jest`` to test our back-end application. 

## Demo Project

So right now, we would be performing a unit test on our code using ``Jest`` testing tool. Let’s begin by installing ``Jest`` package to our code folder.  To complete this, type ``npm install jest`` in the command prompt and when successfully installed, a success message will be displayed.

In this tutorial, we intend to test the efficiency of some selected routes in our Node JS application. This will necessitate writing different unit tests for each routes and evaluating its correctness. Now let’s optimize our file structure in order to successfully unit test our application. 
Navigate to the ``package.json`` file and edit it to include this. 
 

```
javascript

"scripts": {
    "test": " jest",
    "start": "nodemon index.js"
  },

```

 The code above includes Jest package as the default recognized testing application whenever we want to run some performance testing on this project. This automatically triggers jest functionality when we enter npm test in the ``command prompt``.
 
Thereafter, we would like to create our test environment. A folder in the ``root`` directory should be created with the name “tests”. This helps the Jest operator to locate the files for testing. Within the test folder, kindly create a test file. The file can be named with whatever name you prefer but the suffix ``.test.js`` should be added so as to enable ``Jest`` recognize it and run it while testing.
After completing all these, let’s go into unit testing proper. 

In the”test.js” file, let’s import and initialize some required packages and functions.  In my code, I intend to test the routes of a book library application.  It contains the ``get all book`` route, ``Get a single book`` route, ``upload a book`` route and ``delete a book`` route. . We intend on making unit tests for these routes. 
So firstly, we intend to import the book database into the test.js file.

```

Javascript
const Book = require('../models/Book')

```


The code above imports and initializes our default book MongoDB database.
We would then be importing the functions that we intend to test in each route. 



```
 jsx
const {GetAllBooks}= require("../controllers/Books");

```

The function above is for the get all books route. This contains the function to be tested. Now we intend to go into the Jest test function. 

```
jsx
jest.mock("../models/Book");

const req = {};
const res = {
  status: jest.fn((x) => x),
  send: jest.fn((x) => x),
};

it("it should return all the books in the database", async () => {
  Book.find.mockImplementationOnce(() => ({
    Title: "black is king",
    Author: "black",
    price: "$23",
    Summary: "redkjnsadf",
  }));
  await GetAllBooks(req, res);
  expect(res.status).toHaveBeenCalledWith(200);
  expect(res.send).toHaveBeenCalledTimes(1);
});

```


First of all, Jest offers you the ability to create a fake database by copying the structure of the default database. This is known as mocking. This enables the unit test to operate faster and eliminate the lag that comes with getting responses from large databases. Testing which involves the real database is referred to as end-to-end testing as opposed to unit testing. 
Also, attached above are sample requests and response objects. The response objects contains both the status and send function which returns a defined output if successfully run or not. 

Now the ``It`` function contains a short description of what the test should be about. Also attached to it is an anonymous function containing the request we intend to test. The ``expect`` statement would return passed if the function satisfies the requirements. If it fails, a failed response would be returned. 

## Other Additional Information

With that we have delved a bit into unit testing of functions. You can also attempt testing for the delete functions, upload function and specific book function. 


## Conclusion
So we have been able to harness the usefulness of testing tools in optimizing our web application. We have also enjoyed its simplicity. Other additional features like we mentioned earlier can also be integrated using the same method talked about in this tutorial.
I sincerely hope you learned something new and enjoyed this innovative tutorial. Till next time, keep on coding.