Visual regression testing plays a critical role in ensuring that the visual appearance of a web application remains consistent over time. When dealing with UI components, it can be challenging to catch visual bugs and unintended changes. This is where Storybook, a development environment for UI components, can come to the rescue.

In this blog post, we will explore how to set up visual regression testing using Storybook in a JavaScript project.

What is Storybook?

Storybook is a tool for developing UI components in isolation. It allows developers to build and document reusable components independently before integrating them into an application. Storybook provides a visual playground where components can be displayed with different props, variations, and states.

Setting up Storybook

To start using Storybook, you need to have Node.js and npm (or yarn) installed on your machine. Here’s how you can set up Storybook in your JavaScript project:

1. Navigate to your project directory in a terminal.
2. Run the following command to create a new Storybook project:

npx sb init

1. Follow the prompts to configure Storybook’s initial setup.

Once the setup is complete, you can start adding stories to showcase your components.

Writing Stories for Visual Testing

Stories in Storybook represent different states or variations of your components. Each story is accompanied by a corresponding React component that defines the visual appearance of the component. To enable visual regression testing, we will utilize the addon called Storybook Addon Storyshots.

1. Install the required package by running the following command:

npm install --save-dev @storybook/addon-storyshots

1. In your Storybook configuration file (main.js or preview.js), import and configure the addon:

// main.js or preview.js
module.exports = {
  addons: ['@storybook/addon-storyshots'],
};

1. Create a new file called storybook.test.js (or any other desired name) in your project’s root directory.

2. In storybook.test.js, import the required testing library and configure the visual regression testing:

import initStoryshots from '@storybook/addon-storyshots';

initStoryshots();

Running Visual Regression Tests

To run the visual regression tests, you can add a script to your package.json file:

{
  "scripts": {
    "test:storybook": "storybook test --watch",
    "test:visual": "jest --config='./storybook.test.js'"
  }
}

The test:storybook script starts the Storybook server in watch mode, allowing you to view and interact with your components. The test:visual script executes the visual regression tests using Jest.

You can now run the following command to start the visual regression testing:

npm run test:visual

Conclusion

Visual regression testing with Storybook provides a reliable way to catch UI component regressions and ensure consistent visual appearance. By using the Storybook addon and running tests using Jest, you can easily integrate visual testing into your JavaScript project’s development workflow.

Start leveraging Storybook’s power to develop, document, and test your UI components with confidence!

#javascript #storybook