Javascript

Unit Testing Qwik Components

Published Feb 13, 2023

Updated Feb 13, 2023

5 min read

This article was written over 18 months ago and may contain information that is out of date. Some content may be relevant but please refer to the relevant official documentation or available resources for the latest information.

Unit Testing Qwik Components

Qwik is a new, superfast JavaScript framework from builder.io. Created by Miško Hevery, the author of AngularJS, Qwik aims to deliver instant loading web applications of any size or complexity through resumability. This is accomplished partially by delaying the execution and download of JavaScript for as long as possible while providing an excellent developer experience.

"You know React? You know Qwik."

— qwik.builder.io

Given Miško's background as the creator of AngularJS, it's interesting that writing Qwik feels very similar to writing React. It even has a React compatibility mode. Personally, I have experience using mostly Angular, but I found that developing with Qwik was very smooth and enjoyable.

So, although I am definitely hesitant to jump on new technologies, after attending Miško's workshop, browsing through all the resources at framework.dev tinkering with Qwik, and building a couple of apps with it, I became a fan.

However, being a responsible software developer, I then wanted to add unit tests to my Qwik app. And because Qwik is relatively new, I found out there was little documentation on how to do this. Furthermore, until recently, there were no tools to easily set up and interact with Qwik components in unit tests. But that didn't stop me. I explored, asked, and waited for a PR to be merged, and now I am proud to present a comprehensive guide to unit testing Qwik apps. So, without further ado, let's dive into setting up our testing environment.

Configuring a Testing Environment

There are several options when it comes to choosing a testing framework, and I have even experimented with using Jest, as it is the popular choice for unit testing. However, since Qwik uses Vite, I found that using Vitest was the most straightforward and efficient option. Vitest is specifically designed to be the go-to test runner for Vite projects, which makes it a great fit.

If you are familiar with Jest, you will be happy to know that the Vitest API is very similar, so you won't have to learn much to use it effectively.

Before moving further to the actual setup, let's make sure you have a Qwik project to test. If you don't yet, you can simply create one by running npm create qwik@latest.

Now, let's set up vitest in our Qwik project. It takes 3 easy steps:

Install Vitest as a dev dependency by running npm i vitest --save-dev from the root of your project. This will update the devDependencies array in your package.json file.
Update your vite.config.ts file to include a test configuration in the defineConfig function. You can start with an empty object for now, but you can always add configuration options later on. Your vite.config.ts should look something like this:

// ./vite.config.ts
import { defineConfig } from 'vite';
import { qwikVite } from '@builder.io/qwik/optimizer';
import { qwikCity } from '@builder.io/qwik-city/vite';
import tsconfigPaths from 'vite-tsconfig-paths';

export default defineConfig(() => {
  return {
    plugins: [qwikCity(), qwikVite(), tsconfigPaths()],
    preview: {
      headers: {
        'Cache-Control': 'public, max-age=600',
      },
    },
    test: {}, // this is the config entry we are adding
  };
});

Update the "scripts" section of your package.json file to include commands for running vitest once, running it in watch mode, and for generating coverage reports. Your "scripts" section should look something like this:

"scripts": {
    ...
    "test": "vitest --run",
    "test.watch": "vitest",
    "coverage": "vitest run --coverage"
}

After completing these steps, you should be able to run npm run test and npm run coverage from your terminal to use Vitest.

Note that if you run npm run test and you don't have any tests yet, which is likely the case at this point, you will see the message No test files found, exiting with code 1. Don't worry. We are about to add some tests shortly.

Writing Tests

By default, vitest will look for files with names that match the pattern '**/*.{test,spec}.{js,mjs,cjs,ts,mts,cts,jsx,tsx}. In a Qwik project that uses TypeScript and returns JSX elements, it makes sense to use the *.spec.tsx or *.test.tsx pattern. I prefer to use the.spec suffix. But .test works just as well, and is equally valid. Feel free to choose the one that you like best.

To proceed with writing a unit test, we will need a component to test. For this example, we will use a simple counter component that has a div that displays a number and a button that increments it. To create the component, follow these steps:

Go to the src/components directory, and create a new folder called counter.
Inside the counter folder, create a new file called counter.tsx and add the following code:

import { component$, useStore } from "@builder.io/qwik";

export const Counter = component$(() => {
  const state = useStore({
    count: 0,
  });

  return (
    <>
      <button class="increment" onClick$={() => state.count++}>
        +
      </button>
      <div class="count">{state.count}</div>
    </>
  );
});

Next to the counter.tsx file, create a new file called counter.spec.tsx file next to it. This file will contain the unit tests for the Counter component.

Now that we have our component and our test file, we can proceed to write our unit tests. Let's open counter.spec.tsx and add some boilerplate along with a simple test to verify we have everything set up correctly:

import { describe, expect, it } from "vitest";
import { Counter } from "./counter";

describe("Counter component", function () {
  it('should assert true', async () => {
    // this should always pass
    expect(true).toBe(true);
  });
});

We have a describe method that groups related tests together (in our case, we're grouping all the tests we will write for our Counter component), an expect method which is used to make assertions about the values returned by the code being tested, and an it method that defines an individual test.

If we now run npm run test, we should see the following output:

 Test Files  1 passed (1)
      Tests  1 passed (1)

Writing a Simple Test Case

Now that we verified that our dummy test work, let's actually test our component's behavior. First, we want to test that it renders correctly, so we will remove our dummy test and leverage the new createDOM method from @builder.io/qwik.testing to render our Counter component inside the test:

import { createDOM } from "@builder.io/qwik/testing"; // import the createDOM method
import { describe, expect, it } from "vitest";
import { Counter } from "./counter";

describe("Counter component", function () {
  it("should render", async () => {
    // create the component's DOM and get back the container and a render method
    const { screen, render } = await createDOM();

    // call the render method with the JSX node of our Counter component as a parameter
    await render(<Counter />);

    // get the div that displays the count from our container
    const countElement = screen.querySelector(".count");

    // assert the displayed count is "0" which is the default value
    expect(countElement?.textContent).toBe("0");
  });
});

Rerunning the test should result in a pass if we did everything correctly. Now we know our component does render and displays zero as the count.

Testing Interactions

"Great," you say, "but I want to test the component's logic, not just the initial render!". Well, you're in luck because the createDOM method returns one more property - userEvent - that you can use to interact with the component's DOM. This allows us to simulate user interactions, such as clicking a button, and test whether the component responds correctly.

For example, we can test whether our counter correctly increments the count by clicking the button. Here is the updated code example:

  it("should increment on click", async () => {
    // we retrieve the `userEvent` method along with `screen` and `render`
    const { screen, render, userEvent } = await createDOM();

    // render the component
    await render(<Counter />);

    // get the div that displays the count from our container
    const countElement = screen.querySelector(".count");

    // assert the displayed count is "0" which is the default value
    expect(countElement?.textContent).toBe("0");

    // pass a selector that matches the increment button as a first parameter 
    // and the name of the event we want to trigger ("click") as the second parameter
    await userEvent("button.increment", "click");

    // assert the displayed count is now incremented from 0 to 1 
    expect(countElement?.textContent).toBe("1");
  });

With this additional test, we can be confident that our Counter component not only renders correctly, but also updates the count as expected when the increment button is clicked. Voilà, our component's behavior has been verified!

Mocking Qwik Hooks

So far, we have a test that verifies the component's logic, which is great! However, there may come a time when we need to mock parts of the component's logic to test certain scenarios. Unfortunately, here comes a little trade-off for the sake of Qwik's quickness. The component$ wrapper does not expose the internals of the component, so we cannot easily modify it for our tests.

Fortunately, the most common thing we need to mock in Qwik components are hooks such as useLocation() or useStore(). We can do this by using vi.mock. As we can read in the Vitest docs, the vi.mock method takes two arguments: the path to the module that we want to mock, and a function that returns the mocked module.

For example, if we want to modify the initial count in our useStore() hook to be 1, we can mock the entire @builder.io/qwik module and return the actual module with the modified initial value. We can use the JavaScript bind method to do this. The call to vi.mock can be placed anywhere in the code as it is hoisted and will always be called before modules are imported, but for clarity, we will put it in a beforeAll block:

import { createDOM } from "@builder.io/qwik/testing";
import { describe, expect, it, vi, beforeAll } from "vitest";
import { Counter } from "./counter";

beforeAll(() => {
  // mock useStore to start with count of 1 instead of 0
  vi.mock("@builder.io/qwik", async () => {
    const qwik = await vi.importActual<typeof import("@builder.io/qwik")>(
      "@builder.io/qwik"
    );
    return {
      ...qwik, // return most of the module unchanged
      // leverage bind to set the initial state of useStore
      useStore: qwik.useStore.bind("initialState", { count: 1 }),
    };
  });
});

describe("Counter component", function () {
  it("should increment on click", async () => {
    // we retrieve the `userEvent` method along with `screen` and `render`
    const { screen, render, userEvent } = await createDOM();

    // render the component
    await render(<Counter />);

    // get the div that displays the count from our container
    const countElement = screen.querySelector(".count");

    // assert the displayed count is "1" - the default value set by our mock
    expect(countElement?.textContent).toBe("1");

    // pass a selector that matches the increment button as a first parameter 
    // and the name of the event we want to trigger ("click") as the second parameter
    await userEvent("button.increment", "click");

    // assert the displayed count is now incremented from 1 to 2
    expect(countElement?.textContent).toBe("2");
  });
});

Mocking the useLocation hook is even simpler, as it is not expected to change during a test. In this case, we can directly return an object from the mock. Here is an example of how to mock the useLocation hook:

vi.mock("@builder.io/qwik", async () => {
  const qwik = await vi.importActual<typeof import("@builder.io/qwik")>(
    "@builder.io/qwik"
  );
  return {
    ...qwik,
    // return a hardcoded object for every useLocation call
    useLocation: {
      params: {},
      href: "/mock",
      pathname: "mock",
      query: {},
    }
  };
});

Conclusion

As a newcomer to the world of JavaScript frameworks, Qwik offers a unique approach to building fast, efficient web applications. However, we shouldn't forget about the quality and robustness of our code. In this blog post, we provided a comprehensive guide on how to set up and write tests for your Qwik components.

Setting up a testing environment for a Qwik app is relatively straightforward. Qwik uses Vite as its build tool, which means that the most efficient option for unit testing is to use Vitest, a test runner specifically designed for Vite projects. We showed how to install Vitest and update the Vite config file to include a test configuration, and went through examples of how to write tests for Qwik components, including how to mock hooks and test interactions with the DOM.

By following the steps and examples in this post, you can easily add unit tests to your Qwik app, and ensure that your components are working correctly. This will give you confidence in your code, and allow you to build more complex and robust applications with Qwik. And if you found this article a bit overwhelming, do not worry, you can check out the Qwik starter kit which includes examples of already implemented tests.

Have fun writing Qwik and reliable apps!

This Dot is a consultancy dedicated to guiding companies through their modernization and digital transformation journeys. Specializing in replatforming, modernizing, and launching new initiatives, we stand out by taking true ownership of your engineering projects.

We love helping teams with projects that have missed their deadlines or helping keep your strategic digital initiatives on course. Check out our case studies and our clients that trust us with their engineering.

About the author(s)

Jan Kaiser
Software engineer passionate about everything web-related. Particularly loves Angular, SCSS, TypeScript, soccer and dachshunds
@honzikec @honzikec

Using React In Your Qwik Application

Introduction React, developed by Meta, is a JavaScript library for building user interfaces, and it is one of the most used UI JavaScript libraries in the world. React will be turning a decade old by May 2023. It has gained a lot of popularity over the years, and its latest version, React 18, was released in March 2022. Qwik is a new JavaScript framework by Misko Hevery, creator of Angular, for building frontend browser applications. The major benefit of Qwik is its performance optimization, which features resumability and lazy loading. As it stands now, there are virtually no Qwik third-party packages or libraries that currently exist, but luckily the Qwik team factored this in, making it easy for developers to easily integrate React libraries or your old React components into your Qwik project without too much difficulty. In this article, I will show you how to easily integrate React libraries or components into your Qwik project. Project Set Up To get started, we need to create a new Qwik app. We can do this by running the following command in our terminal: ` You can also get additional tools and configurations using our starter.dev kit by running the command in your terminal: ` You will be prompted to enter the name of your project (let’s call it qwik-react), choose the default option when asked to select a starter, and then install npm dependencies. Now we have our Qwik application ready to go. Let’s start the development server and see what it looks like; ` Now that our app is up and running we will see how we can integrate a React package and component into our Qwik project. Integrating React in Qwik Like most JavaScript frontend libraries or frameworks, React makes use of hydration, which has its drawbacks and might be more expensive than you think. Qwik needs no hydration on load. It’s just pure HTML. This makes Qwik qwiker to load UIs, with which users can start interacting. You should keep this in mind when considering to include React components in your Qwik applications. QwikReact is a tool that allows you to use React components in Qwik, including the whole ecosystem of component libraries such as Material UI, Threejs and React Spring. To get started, we need to run this command inside our Qwik app: ` This will install needed dependencies such as qwik-react, react, and react-dom. It will also add emotion and mui, which you can uninstall if you don’t intend to use them. If we check our project, we should now have some new folders generated. The most important is the src/integrations/react. This is where all our React components will be implemented or React packages will be used. Qwikify$ The qwikify$ function is exported from @builder.io/qwik-react, which converts React components into Qwik components that you can use across your application, and allows Qwik to implement partial hydration of React components. You cannot use React components in Qwik without converting them first to remove React’s hydration pattern, which is not supported in Qwik, using qwikify$(). Another important thing to remember is to make sure the file containing your React component has this; ` This needs to be imported at the top of the file as this serves as instructions to the compiler to use React as the JSX factory. This means you cannot mix your React components with a Qwik component. The code above is from the Qwik demo. You can see how the React components are wrapped with the qwikify$() function. If your React package requires some configuration, don’t try to pass it as a props. Instead, do every configuration right inside the file, ensuring only the dynamic data is passed through. The code above is from our Qwik GitHub showcase. Check out the full source code here. So once you are done with Qwikifying your React component, you can now import and use it just as you would normally do a Qwik component. Let’s run our application, and navigate to the React page at ` to view the default Qwik demo; ` Interactivity Qwik tries to reduce or completely remove hydrations, but React heavily depends on it. This means we have to find a way to hydrate our React Component without affecting the concept of Qwik. Qwik allows you to decide when to hydrate your components by using the client: JSX properties. This technique is commonly referred to as “partial hydration”. For more information on this checkout Adding Interactivity on Qwik Docs. Conclusion In this article, we saw how to convert React to a Qwik component. We also learned about the dos and don’ts of using React in Qwik, as well as how to handle hydration. I hope you enjoyed this article. Thank you for reading! If you have any questions or run into any trouble, feel free to join the discussions going on at starter.dev or on our Discord....

Nov 25, 2022

5 mins

Qwik

How to Setup Storybook in a Qwik Project

Introduction Storybook is a great tool for testing and visualizing your components in different states. In this article, we will see how to setup Storybook in a Qwik project. Qwik Qwik is a new JavaScript framework by Misko Hevery, creator of Angular, for building frontend browser applications. The major benefit of Qwik is its performance optimization, and this is achieved through zero loading, resumability, lazy loading, reduced rendering, scalability, and code once. For more information on Qwik, you can check out the docs, github repo, and discord. Project Set Up To get started, we need to create a new Qwik app. We can do this by running the following command in our terminal: ` Initialize Storybook Storybook, unfortunately, doesn’t have a Qwik template yet because it is a new Framework. So the work around is to use the html template . Using the command below, we can initialize Storybook: ` During the initialization, Storybook would ask to automatically install some optional dependencies such as; EslintPlugin and npm7, you can accept or reject it. To accept, type y and hit Enter to progress. Storybook would try to setup a default stories folder, which is based on the ` template we choose, which is `. It is not compatible with the Qwik compiler and will result in compilation errors, so we will have to delete it to avoid running into such errors. Project Structure Our project structure is already setup by Qwik, and Storybook initialization has created a .storybook folder. But we need to make some changes to the Storybook file extension since our project is in TypeScript. This is a snippet of the folders in our project: ` Configuring Storybook Since Qwik runs on Vite, we need to set up the viteFinal function in our main.ts file, which will give us the config that we will use to register our Qwik Vite plugin. Add this line of code in the configuration object: ` In the preview.ts file, this is where we configure how Storybook renders our stories. We need to execute Qwikloader. This will help in registering global browser events, and much more Qwik related benefits. We will replace the content in the file with the code below: ` This solution was found in this discussion: How to do component testing with Qwik?. I believe when the Qwik Storybook type template becomes available these configurations will be there by default. Now we are done with the configuration, let's run storybook and see what we have: ` Creating Stories We can create our first story, we will create a story for our Qwik app component. We will create this story for our default Qwik Header component. I modified the Header component to accept a menus props: ` Conclusion In this article, we saw how to setup Storybook in a Qwik project. We also saw how to create our first story. I hope you enjoyed this article. Thanks for reading. If you don't want to do these steps yourself, check out our starter.dev Qwik kit that already has Storybook enabled for your use here. A link to the project repo can be found here. If you have any questions or run into any trouble, feel free to reach out on Twitter....

Dec 12, 2022

3 mins

Qwik

Understanding the Difference Between `:focus` and `:focus-visible` in CSS

Understanding the Difference Between :focus and :focus-visible in CSS I have learned my fair share about the importance of keyboard accessibility, so I know that visual indication of the focused element is very important. But the well-known :focus pseudo-class is not always the best fit for this job. That's where :focus-visible comes in. Let's look at the differences between these two pseudo-classes and explore the best practices for using them effectively. What is the :focus Pseudo-Class? The :focus pseudo-class is a CSS selector that applies styles to any element that receives focus, regardless of how that focus was triggered. This includes focus events from keyboard navigation, mouse clicks, and touch interactions. Example Usage of :focus ` In this example, the button will display a blue outline whenever it is focused, whether the user clicks on it with a mouse, taps it on a touchscreen, or navigates to it using the keyboard. What is the :focus-visible Pseudo-Class? The :focus-visible pseudo-class is more specialized. It only applies styles to an element when the browser determines that the focus should be visible. This typically occurs when the user navigates via the keyboard or assistive technologies rather than through mouse or touch input. Example Usage of :focus-visible ` Here, the button will only show a blue outline when focused through keyboard navigation or another input method that usually requires visible focus indicators. Key Differences Between :focus and :focus-visible :focus - Behavior: Applies to any element that receives focus, regardless of the input method. - Use Cases: Ensures that all interactions with the element are visually indicated, whether by mouse, keyboard, or touch. :focus-visible - Behavior: Applies styles only when the focus should be visible, such as using a keyboard or assistive technology. - Use Cases: Ideal for scenarios where you want to provide focus indicators only to keyboard and assistive technology users while avoiding unnecessary outlines for mouse and touch users, typically required by design. Accessibility Implications :focus - Pros: - Guarantees that all users can see when an element is focused, which is critical for accessibility. - Cons: - Can lead to a suboptimal experience for mouse users, as focus styles may appear unnecessarily during mouse interactions. :focus-visible - Pros: - Enhances user experience by showing focus indicators only when necessary, thus keeping the interface clean for mouse and touch users. - Tailors the experience for keyboard and assistive technology users, providing them with clear visual cues. - Cons: - Additional considerations may be required to ensure that focus indicators are not accidentally omitted, especially in older browsers that do not support :focus-visible. - There may be cases where you want to show focus indicators for all users, regardless of input method. Best Practices for Using :focus and :focus-visible To achieve the best accessibility and user experience, combining both :focus and :focus-visible in your CSS is often a good idea. Combining :focus and :focus-visible ` Here is a Stackblitz example of what such styling could look like for you to try out and play with. Additional Tips - Test with Keyboard and Assistive Technology: Ensure that your web application is navigable using a keyboard (Tab, Shift + Tab, etc.) and that focus indicators are visible for those who rely on them. It's never a bad idea to include accessibility testing in your e2e testing suite. - Provide Clear Focus Indicators: Make sure that focus indicators are prominent and easy to see. A subtle or hard-to-spot focus indicator can severely impact accessibility for users who rely on keyboard navigation. Conclusion The :focus-visible pseudo-class offers a more refined way to manage focus indicators, improving accessibility and user experience, particularly for keyboard and assistive technology users. By understanding the differences between :focus and :focus-visible, and applying best practices in your CSS, you can create more accessible and user-friendly web applications. Remember, accessibility should never be an afterthought. By thoughtfully applying focus styles, you ensure that all users, regardless of how they interact with your site, can easily navigate and interact....

Nov 8, 2024

3 mins

AccessibilityCSSPlaywright

Learning Paths for Next.JS Developers with Ankita Kulkarni

In this video, Rob Ocel and co-hosts Tracy Lee, Adam Rackis, and Danny Thompson talk with tech educator Ankita Kulkarni about her journey from engineering leader to full-time educator. Ankita shares insights on teaching Next.js, bridging practical knowledge gaps, and helping developers tackle real-world challenges. They discuss Next.js as a React-based framework, its benefits, and the challenges it presents for beginners. Chapters - Introduction to the Podcast and Guests 00:01 - Meet Ankita Kulkarni, Tech Educator 00:26 - Ankita's Transition to Full-Time Education 01:41 - Teaching Practical Knowledge in Next.js 03:19 - Effective Methods for Teaching Next.js 05:27 - Challenges of Being a Full-Time Educator 07:48 - Balancing Broad and Specific Examples 09:54 - Embracing Mistakes as a Teaching Tool 12:13 - Pair Programming and Mentorship 14:00 - Discussion on Next.js and Framework Adoption 16:48 - Advantages and Challenges of Next.js 18:12 - Choosing the Right Framework for Your Needs 20:35 - Impact of Next.js in React Documentation 22:26 - Learning Paths for New Developers 23:24 - The Rise of Full-Stack Web Development 25:09 - Benefits of Frameworks Abstracting Complexity 26:27 - OpenNext and Deployment Flexibility 28:06 - Ankita's Excitement for New Next.js Features 30:35 - The Future of Next.js Without Vercel 32:16 - Final Thoughts and Where to Find Everyone Online 34:21 Follow Ankita Kulkarni on Social Media Twitter: https://x.com/kulkarniankita9 YouTube: https://www.youtube.com/@kulkarniankita Sponsored by This Dot: thisdot.co...

Nov 12, 2024

2 mins

NextJSJavaScript

Let's innovate together!

We're ready to be your trusted technical partners in your digital innovation journey.

Whether it's modernization or custom software solutions, our team of experts can guide you through best practices and how to build scalable, performant software that lasts.

Unit Testing Qwik Components

Unit Testing Qwik Components

Configuring a Testing Environment

Writing Tests

Writing a Simple Test Case

Testing Interactions

Mocking Qwik Hooks

Conclusion

Jan Kaiser

You might also like

Using React In Your Qwik Application

How to Setup Storybook in a Qwik Project

Understanding the Difference Between `:focus` and `:focus-visible` in CSS

Learning Paths for Next.JS Developers with Ankita Kulkarni

Let's innovate together!

You might also like

Using React In Your Qwik Application

How to Setup Storybook in a Qwik Project

Understanding the Difference Between `:focus` and `:focus-visible` in CSS

Learning Paths for Next.JS Developers with Ankita Kulkarni