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Stencil is a library for building reusable, scalable component libraries. You can test Stencil components directly in a real browser using WebdriverIO and its browser runner.


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

// wdio.conf.js
export const config = {
// ...
runner: ['browser', {
preset: 'stencil'
// ...

In case you use Stencil with a framework like React or Vue, you should keep the preset for these frameworks.

You can then start the tests by running:

npx wdio run ./wdio.conf.ts

Writing Tests​

Given you have the following Stencil component:

import { Component, Prop, h } from '@stencil/core'

tag: 'my-name',
shadow: true
export class MyName {
@Prop() name: string

normalize(name: string): string {
if (name) {
return name.slice(0, 1).toUpperCase() + name.slice(1).toLowerCase()
return ''

render() {
return (
<div class="text">
<p>Hello! My name is {this.normalize(}.</p>

In your test use the render method from @wdio/browser-runner/stencil 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.:

import { expect } from '@wdio/globals'
import { render } from '@wdio/browser-runner/stencil'

import MyNameComponent from './components/Component.tsx'

describe('Stencil Component Testing', () => {
it('should render component correctly', async () => {
await render({
components: [MyNameComponent],
template: () => (
<my-name name={'stencil'}></my-name>
await expect($('>>>.text')).toHaveText('Hello! My name is Stencil.')

Element Updates​

If you define properties or state in your Stencil component you have to manage when these changes should be applied to the component to be re-rendered. For that use the flushAll method that is returned from the render method, e.g.:

const { flushAll } = render({
components: [AppLogin],
template: () => <app-login />

// update component state via
await $('...').click()


// assert after update
await expect($('...')).toHaveElementClass('...')

If you prefer to apply changes automatically, set the autoApplyChanges flag, e.g.:

const { flushAll } = render({
components: [AppLogin],
template: () => <app-login />,
autoApplyChanges: true
// update component state and assert immediatelly
await $('...').click()
await expect($('...')).toHaveElementClass('...')


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

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