Cypress Component Testing vs React Testing Library

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CCT vs RTL talks about the similarities between the tools, the differences, compares the ways of doing the same things with the tools, and finally gives a developer experience comparison demo.

This talk has been presented at TestJS Summit 2023, check out the latest edition of this JavaScript Conference.

FAQ

Cypress offers a superior developer experience by leveraging a real browser environment that allows inspection and debugging directly through DevTools, providing immediate feedback and detailed insights into component behavior. React Testing Moibrary, while effective for testing, relies on terminal outputs that may not provide as much detail or immediate feedback.

Cypress Intercept provides a simpler and more flexible API for managing network requests, allowing changes in intercepts directly within test blocks. Mock Service Worker, while robust, requires more setup and lacks the ability to modify handlers within individual tests, making Cypress more suitable for dynamic test scenarios.

Cypress Component Testing provides a real browser environment with full access to DevTools and network activities, enhancing observability and debugging capabilities. React Testing Library, on the other hand, operates within the terminal using HTML outputs, which may limit direct interaction with component states and behaviors.

Cypress Component Testing allows you to mount components in a manner similar to how they are mounted in your application, using custom mounts to simplify complexities, thus enabling a more realistic testing environment.

Both Cypress and Jest offer spying and mocking capabilities, but they differ in implementation. Cypress uses a more declarative approach with simple syntax, while Jest requires more setup and often a more detailed, imperative approach to achieve similar outcomes.

Murat K Ozcan
Murat K Ozcan
25 min
11 Dec, 2023

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Video Summary and Transcription
The Talk discusses the differences between Cypress component testing and React Testing Library (RTL). It highlights the benefits of using Cypress Component Testing, such as easier handling of complex components and a more stable testing experience in CI. The comparison between SignOn and Jest focuses on low-level spying and mocking capabilities. The comparison between Cypress Intercept and Mock Service Worker (MSW) examines their network spy and mocking capabilities. The Talk also emphasizes the superior developer experience and observability provided by Cypress component testing compared to RTL.

1. Cypress Component Testing vs React Testing Library

Short description:

Hello, everyone. My name is Murat, and today I'll be talking about Cypress component testing versus React Testing Library. We've been using Cypress Component Testing at X10, my company, for one year, and we've been doing end-to-end tests for two years. In React, you may run into the situation where you have to wrap your component with many providers. This is a Cypress Component Test for a simple component from the book. Here's the second example, it's a text field, we're typing into it, it can also be read-only. On the left, Cypress, when we're mounting the component, we use site.stop instead and alias. Here is the third component, you're clicking on each one and ensuring that we're in a certain route and we want to make sure that the thing we click on is highlighted and the things we don't click on are not highlighted. The more complex the component gets, the more benefit you will have from the Cypress API and you will have a little less code accomplishing the same thing. But the real seller is the HTML versus browser.

Hello, everyone. My name is Murat, and today I'll be talking about Cypress component testing versus React Testing Library. You can find a copy of the presentation on Slides.com.

My name, SciCT versus RTL. Let's get started. The four topics in the presentation, Cypress component versus React Testing Library examples, low-level spying and mocking comparison, network-level spying and mocking comparison, and finally, a comparison of the developer experience. We've been using Cypress Component Testing at X10, my company, for one year, and we've been doing end-to-end tests for two years. We also have React Testing Library in there, too, so you are able to make some calculated comparisons between the two. All examples in the presentation will be from my book, Cypress Component Test Driven Design. With each component, you'll see a Cypress Component Test variant versus a React Testing Library variant, which you can compare yourselves when you produce the code.

In React, you may run into the situation where you have to wrap your component with many providers. When you are having a Cypress Component Test or a React Testing Library test, you have to mount the component the same way it's being mounted in your application, so for that you can use these custom mounts, which let you abstract away some of the complexities that you don't really have to think about when you're testing your component. The idea is from Kent Dodd's EPIC React, and you'll see pretty much the same code over here, and we'll compare how they're being used with different components. This is a Cypress Component Test for a simple component from the book, just showing you this is testing two of Heroes right over here. Let's take a look at the code, sizect on the right side, rtl on the left side, for mounting or rendering, that's the same way, in rtl we have right to left variable assignment and the assertions on that. Cytus, we have left to right chain syntax and similar assertions. We have the within API over in rtl, and it's a similar API on the Cypress site. At the end it's the same test, just slightly different APIs accomplishing the same thing. Here's the second example, it's a text field, we're typing into it, it can also be read-only. Then in the test, we want to make sure that onChange calls are being made as we're typing into the thing. The only distinction here is how we're marking the onChange, so just FN for onChange and then we're making sure that assignment is being done when we're mounting the component and then later on we make assertions on that component that it's being called so many times. On the left, Cypress, when we're mounting the component, we use site.stop instead and alias, later on we refer to the alias this way and then ensure that it's called so many times as we're typing into the field. Other than that, on the right side I also use testing library so we have find by placeholder text, over here we can compare that one on one, then we can see the API differences for ourselves. Here is the third component, you're clicking on each one and ensuring that we're in a certain route and we want to make sure that the thing we click on is highlighted and the things we don't click on are not highlighted. With Cypress, we have this jQuery convenience so we can click on something and verify that things are having a certain CSS and the things we don't click on don't have that CSS. It's possible to do the same thing on the RTL side but takes a little bit of work. And you'll see this pattern, the more complex the component gets, the more benefit you will have from the Cypress API and you will have a little less code accomplishing the same thing. But the real seller is the HTML versus browser. So on the React testing library side, you have things in the terminal, you basically have just HTML as text. And on the Cypress component testing side, you have the real browser, you have dev tools, you have network, everything that you have in your real application, but just with your component being mounted.

2. Cypress Component Tests vs RTL Examples

Short description:

So in Cypress, we can easily get the window object and call the get current position method with a fake position object. However, in RTL, we need to do some extra work to achieve the same result.

So that gives you plenty of observability into what's happening with it. If you've been through Epic React, you will like this one, because when I went through it, I created a Cypress component test mirror of all of these examples that Kent covers. And I picked three over here for us to take a look at together. So here's a simple Redux example. The way we're rendering or mounting with the Redux provider and the store is exactly the same. If you want to have a custom store, the way we're making an assignment is exactly the same. So nothing is different when it comes to Redux. With Ally, there's slightly different APIs because these are custom libraries at the end. The Cypress, the inject X, and the check Ally. With RTL, we get the container out of there and then make sure that it has no violations. The API is more nuance, a little different, when you want to have custom include impacts like modern or serious, you have to do a little bit of work over on the RTL side, but it's possible to accomplish the same thing. Geolocation is interesting because with Cypress we can just get the window out of the window object and from window navigator geolocation, the get current position method can be started to be called with this fake position object, and you can see the nice abstraction over there exactly communicating what we want to do, with just an RTL there's some work over there, so first we have to just fn the geolocation, and on top of that, after doing that get current position just fn, we have to mark the implementation saying that this is going to be a promise that takes a callback, that takes that fake position as an argument. So it takes a little bit of work, but on top of that we have to have this utility function that's simulating a deferred promise, because we have to act, and then resolve, and await that promise, and then make assertion. So again, it's possible to do the same thing on the RTL side, but it takes a little bit of work to accomplish the purpose. So those are some Cypress component tests versus RTL examples.

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