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Svelte

Svelte is a radical new approach to building user interfaces. Whereas traditional frameworks like React and Vue do the bulk of their work in the browser, Svelte shifts that work into a compile step that happens when you build your app. You can test Svelte components directly in a real browser using WebdriverIO and its browser runner.

Setup​

To setup WebdriverIO within your Svelte project, follow the instructions in our component testing docs. Make sure to select svelte as preset within your runner options, e.g.:

// wdio.conf.js
export const config = {
    // ...
    runner: ['browser', {
        preset: 'svelte'
    }],
    // ...
}
info

If you are already using Vite as development server you can also just re-use your configuration in vite.config.ts within your WebdriverIO config. For more information, see viteConfig in runner options.

The Svelte preset requires @sveltejs/vite-plugin-svelte to be installed. Also we recommend using Testing Library for rendering the component into the test page. Therefor you'll need to install the following additional dependencies:

npm install --save-dev @testing-library/svelte @sveltejs/vite-plugin-svelte

You can then start the tests by running:

npx wdio run ./wdio.conf.js

Writing Tests​

Given you have the following Svelte component:

./components/Component.svelte
<script>
    export let name

    let buttonText = 'Button'

    function handleClick() {
      buttonText = 'Button Clicked'
    }
</script>

<h1>Hello {name}!</h1>
<button on:click="{handleClick}">{buttonText}</button>

In your test use the render method from @testing-library/svelte to attach the component to the test page. To interact with the component we recommend to use WebdriverIO commands as they behave more close to actual user interactions, e.g.:

svelte.test.js
import expect from 'expect'

import { render, fireEvent, screen } from '@testing-library/svelte'
import '@testing-library/jest-dom'

import Component from './components/Component.svelte'

describe('Svelte Component Testing', () => {
    it('changes button text on click', async () => {
        render(Component, { name: 'World' })
        const button = await $('button')
        await expect(button).toHaveText('Button')
        await button.click()
        await expect(button).toHaveText('Button Clicked')
    })
})

You can find a full example of a WebdriverIO component test suite for Svelte in our example repository.