Why Does My React App Need TDD?

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When planning your next app development project make sure you choose the most effective approach to saving time, meet your budget, and get a flawless product.

Test-driven development or TDD is an approach for React development that has proven its worth with countless happy customers over the years including multinationals like Volkswagen, Mastercard, Lenovo, etc. The question on everyone's mind is - are the benefits of applying TDD worth the time and money? What are the best tools to set up test-driven development on my project? And that's exactly what our study aims to answer.

What’s test-driven development?

Test-driven development is a type of software development that focuses on product quality and aims to reduce the cost of changing produced software systems by writing tests first and committing early and often — as opposed to writing code first and then seeing if it passes the standardized unit tests.

The easiest way to explain how Test-Driven Development works is to imagine a three-step process: Red, Green and Refactoring.

Red

Red: The first step starts with developers describing the work scenario in a test. Then they create the objects required so the code compiles, run the test, and see a red bar because the test fails.

Green

Green: Now developers need to write code that can pass the test. This code doesn’t have to be perfect. The only criterion is its ability to pass the test.

Refactor

Refactor: Once the code passes the test, developers can refactor it. After refactoring, developers run the test one more time to make sure they didn’t break anything during refactoring.

Benefits of test-driven development for React apps

Test-driven development can be a new approach for some teams, but it comes with many benefits. Let’s take a look at what these are.

High-quality code

Recently, developers have started to test their code before it is written. ​Without any coding taking place, the main ethos of the testing process is to ​identify gaps in existing code and suggest ways of improving upon them. The ​software then ensures that all concerns are properly addressed.

Another advantage of this method is that when developers start creating new code, they can easily spot what might be missing or otherwise out-of-order. Making sure everything aligns atop an already well-architected platform will result in higher quality software overall.

Cut costs

When it comes to React app development, using the Test-driven development method helps to reduce costs by influencing the following:

  • Scope of work. One of the most common reasons for a constantly growing scope of work is a lack of proper documentation. It’s hard for programmers to estimate how much time a certain feature will take to complete when they don’t have all the requirements, which typically results in buggy software and a lot of back-and-forths. TDD solves this problem because it ensures that there are no gaps in functionality due to rapidly growing codebases (also known as technical debt ). This allowed engineers to handle features more independently and better understand the actual scale of what is being worked on at any given time.
  • Quality of code. High-quality code not only works seamlessly and leads to a bug-free app or product. It also saves money on code support and maintenance. If your app has 100% coverage, you can easily add new functionality without breaking things.
  • There is no amount of rework that can be done to correct a problem without knowing what's wrong. When using a common linear workflow, code can be written before all the requirements are made clear. When following TDD, each team member will have to clarify all technical and business requirements to create tests so everyone involved knows exactly what they're building, avoiding any misunderstandings or unnecessary corrective work after the fact.

Simple debugging

Test-driven development promotes good coding principles such as Don’t Repeat Yourself (DRY), Keep It Simple, Stupid! (KISS), You Ain’t Gonna Need It (YAGNI), and many others.

These principles encourage developers to write clean, well-organized, and easy to read code. By creating easily manageable code it will only take the programmer less time to debug and fix things if there's an error or if he wants to change something up.

Additionally, high-quality code is easy to work on even if you change your development team or new specialists join the project.

Detailed product documentation 

Tests that developers write on paper before they start coding their applications — and the detailed documentation — can be used as a very clear and concise explanation of exactly how their code works and what it does. Documentation is particularly important for the success of your project in the following cases:

  • Migrating to new technologies. You may decide to migrate your product to another technology stack when you need newer, more powerful libraries, frameworks, or languages. When migrating to new technologies, developers use documentation to make sure they clearly understand how the code works.
  • Replacing a contractor. Sometimes it becomes necessary to replace a software development company working on your project. The new contractor needs to have full access to documentation so that they can get up to speed quickly and smoothly!
  • Product Development. The reason why a lot of entrepreneurs start their products with a minimum viable product (an MVP) is that it allows them to test their business idea and then modify it to meet their customers' needs. Documentation lets the maker add functionality and modify the system without spending too much time getting familiar with it, which can sometimes be a challenge for a developer.

Ensures better code structure

Unit tests need to be modular and should not depend on one another. This means that time can be saved because you won't have to wait for the processing of other tests to start working on a new test. A lot of people think about writing unit tests first for this reason: It helps them plan out their code as they will know before even starting what exactly the function or method is about and how it should work.

Drawbacks of test-driven development for React apps 

Despite all the powerful benefits we’ve described, following this approach comes with drawbacks that might persuade you not to incorporate it into every aspect of your application. We’ll list them out so that you can understand why they are there in the first place and how they may be resolved to allow us to fully reap TDD's many rewards.

Test-driven development takes longer

Instead of writing code immediately, developers following the TDD approach first think through the code architecture. They then create tests, and only after that start writing code that meets those expectations. As a result, you end up with code later than when you follow a traditional approach. However, the code you do get is far cleaner, does exactly what it’s supposed to, and has significantly fewer bugs – both now and in the future – as a result of future changes.

In the long term, the TDD development approach saves you time and money on maintenance, support and further development.

Doesn't help with projects that lack sufficient preparation 

Test-driven development is pretty useful, but it isn't always the most efficient way to develop a product. Making developers create unit tests before they write code can be difficult and time-consuming. That's because before writing the tests, developers (whether you do it yourself or hire people) need to know what features are required for your project so that they will be able to create the tests accordingly.

This means that before moving forward with test-driven development you have to first collect all of your business requirements so that your team can have them readily available when needed.

Need to maintain tests as well as code

There are a lot of tests that go into a product. For every change that is made, it is necessary to update the tests as well. If a developer wanted to change code but had their code checked with a test harness before making the change, they would have to alter both the code and the protocol which gets submitted as part of the latest test set submitted as part of weekly.

TDD is difficult for beginners

Young development teams may face challenges when diving headfirst into unit testing. Unit testing is a time-consuming practice when you have to design tests for code that doesn't even exist yet. Not to mention that inexperienced developers sometimes don't see the importance of rigorous test writing and refuse to follow up with it.

However, more experienced companies are aware of the benefits of unit testing and practice it daily.

The drawbacks can be avoided

All these shortcomings that we have described above aren’t so difficult to overcome. Besides, the outcome is worth it. If you agree, we recommend you take a look at the tools we use to implement test-driven development on reacting projects.

Best tools to support TDD for React development

In this section, we're going to explain how our team uses the tools of the trade on our React projects. We're also going to share how we use them and why they work for us.

Jest

Jest is a JavaScript testing framework that’s easy to use. It has a complete out-of-the-box set of tools that allow for parallelizing test performance.

The Distinct Cloud team uses Jest for unit and integration testing. With Jest, we cover business logic in components, everything related to APIs, and application states with tests.

Although there are some great alternatives to Jest, like Jasmine or Mocha, we prefer Jest because of the following benefits:

  • Zero configuration. Jest has everything you need for almost any JavaScript project out of the box. This means developers can spend minimum time configuring the system.
  • Snapshots allow us to easily keep track of large objects. This is handy if you want to be sure the user interface doesn’t change unexpectedly. Snapshots can live alongside your tests or be embedded inline.
  • Isolation. With Jest, developers can run tests in parallel and this significantly improves testing performance, which is crucial when it comes to software like Jest because testing applications require a lot of running and re-running of tests before we get the desired result to aim for in this sense.
  • Proper documentation: As we all know, Jest is a well-organized instrument with clear and up-to-date documentation, which will help non-JavaScript developers set up testing facilities that they may require within their projects to ensure they produce quality results at all times during development, big or small!

Enzyme

Enzyme, created by Airbnb is a library that simplifies testing React applications by offering convenient functions for rendering components. Enzyme allows you to perform full rendering, simplified rendering, and static rendering.

Our team uses this tool because of its shallow rendering feature which allows us to get a snapshot of a component, abstracting from the implementation of the child components.

If you’re looking for an alternative to Enzyme, we recommend that you try React-testing-library. It also has a range of powerful features for testing components.

Cypress

Cypress is a tool that helps developers and quality assurance engineers check how the client-side of an app interacts with the back end and how different page components interact with each other.

Cypress can be used by businesses to save time and energy since it tests user login, transactions, etc., or any actions that need to go through. To use Cypress, companies can simply run a command in their terminal, which connects the application back to the main site.

Using Cypress for testing is very easy and offers one of the following benefits:

  • Using advanced snapshots in a Cypress test helps a user manage a matrix of a site’s asset states, and helps accelerate build/deployment times when re-testing against major changes.
  • With synchronous testing, Cypress waits for commands and assertions. It doesn't leave any time for you to manually add wait or sleep timers.
  • Extended functionality. Cypress allows developers to control the behaviour of tests/specs, responses, and timers, just like in unit tests.
    If you want to use something other than Cypress for your web tests, that’s OK too!

Wrapping up

A test-driven development approach in a React web app has shown a proven positive effect on the creation of high-quality products in the shortest amount of time possible. Our team believes in this approach and therefore recommend it to startups with the goal of developing a high-quality product.

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