@cypress/mount-utils
v4.1.1
Published
Shared utilities for the various component testing adapters
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@cypress/mount-utils
Note this package is not meant to be used outside of cypress component testing.
This library exports some shared types and utility functions designed to build adapters for components frameworks.
It is used in:
What is a Mount Adapter?
All Component Tests require a component to be mounted. This is generally done with a custom command, cy.mount
by default.
Requirements
All the functionality used to create the first party Mount adapters is available to support third parties adapters. At minimum, a Mount Adapter must:
- Receive a component as the first argument. This could be class, function etc - depends on the framework.
- Return a Cypress Chainable (for example using
cy.wrap
) that resolves whatever is idiomatic for your framework - Call
getContainerEl
to access the root DOM element
In addition, we recommend that Mount Adapters:
- call
setupHooks
to register the required lifecycle hooks for@cypress/mount-utils
to work
Example Mount Adapter: Web Components
Here's a simple yet realistic example of Mount Adapter targeting Web Components. It uses utilities from this package (@cypress/mount-utils
) This is recommended, so your adapter behaves similar to the first party Mount Adapters.
import {
ROOT_SELECTOR,
setupHooks,
getContainerEl
} from "@cypress/mount-utils";
Cypress.on("run:start", () => {
// Consider doing a check to ensure your adapter only runs in Component Testing mode.
if (Cypress.testingType !== "component") {
return;
}
Cypress.on("test:before:run", () => {
// Do some cleanup from previous test - for example, clear the DOM.
getContainerEl().innerHTML = "";
});
});
function maybeRegisterComponent<T extends CustomElementConstructor>(
name: string,
webComponent: T
) {
// Avoid double-registering a Web Component.
if (window.customElements.get(name)) {
return;
}
window.customElements.define(name, webComponent);
}
export function mount(
webComponent: CustomElementConstructor
): Cypress.Chainable {
// Get root selector defined in `cypress/support.component-index.html
const $root = document.querySelector(ROOT_SELECTOR)!;
// Change to kebab-case to comply with Web Component naming convention
const name = webComponent.name
.replace(/([a-z0–9])([A-Z])/g, "$1-$2")
.toLowerCase();
/// Register Web Component
maybeRegisterComponent(name, webComponent);
// Render HTML containing component.
$root.innerHTML = `<${name} id="root"></${name}>`;
// Log a messsage in the Command Log.
Cypress.log({
name: "mount",
message: [`<${name} ... />`],
});
// Return a `Cypress.Chainable` that returns whatever is idiomatic
// in the framework your mount adapter targets.
return cy.wrap(document.querySelector("#root"), { log: false });
}
// Setup Cypress lifecycle hooks.
setupHooks();
Usage:
// User will generally register a `cy.mount` command in `cypress/support/component.js`:
import { mount } from '@package/cypress-web-components'
Cypress.Commands.add('mount', mount)
// Test
export class WebCounter extends HTMLElement {
constructor() {
super();
}
connectedCallback() {
this.innerHTML = `
<div>
<button>Counter</button>
</div>`;
}
}
describe('web-component.cy.ts', () => {
it('playground', () => {
cy.mount(WebCounter)
})
})
For more robust, production ready examples, check out our first party adapters.
Compatibility
| @cypress/mount-utils | cypress | | -------------------- | ------- | | <= v1 | <= v9 | | >= v2 | >= v10 |