cypress-lit


Running cypress component testing on web components and lit elements.

- cypress-lit
- Installation
- Setup
- Examples
- With Lit HTML
- With Native WebComponents
- Contributing

> The below gif is slowed by 10x so you don't miss it 🐢

!Cypress runner showing a component test of a lit element

Installation

``bash
npm i -D cypress-lit
yarn add -D cypress-lit
pnpm i -D cypress-lit
`

$3

The command needs to be imported from the package and added to cypress commands.

`ts


./cypress/support/component.ts

import "./commands";

import { mount } from "cypress-lit";

declare global {
namespace Cypress {
interface Chainable {
mount: typeof mount;
}
}
}

Cypress.Commands.add("mount", mount);
`

When running cypress components testing you will need to specify a custom dev server. This project has tests that use the below configuration.

`ts
// ./cypress.config.ts

import { defineConfig } from "cypress";

export default defineConfig({
component: {
supportFile: "cypress/support/component.ts",
devServer: {
bundler: "vite",
},
indexHtmlFile: "cypress/support/component-index.html",
},
experimentalWebKitSupport: true,
});
`

Examples

There is a collection of tests for:

- Lit Element
- Pure custom elements

$3

You can pass a hit template directly to the mount command.

`ts
// ./cypress/component/lit.cy.ts#L1-L9

import "../../templates/index.css";
import { html } from "lit";
import { LitCounter } from "../../templates/counter-lit";

describe("Lit mount", () => {
it("mounts", () => {
cy.mount<"counter-lit">(html);
cy.get("counter-lit").shadow().contains("h1", "Count is 0");
});
`

$3

If you have custom elements defined using pure browser javascript then you can pass in a string.

`ts
// ./cypress/component/web-component.cy.ts#L1-L9

import "../../templates/index.css";
import { WebCounter } from "../../templates";

describe("Web Component mount", () => {
it("mounts", () => {
cy.mount<"counter-wc">();
cy.get("counter-wc").shadow().contains("h1", "Count is 0");
});

`

When using custom elements and you need to access the element to set non-string attributes you can do this using the properties option:

`ts
// ./cypress/component/web-component.cy.ts#L26-L39

it("can pass emitters as spies", () => {
cy.mount<"counter-wc">(
count=${42}
>,
{ properties: { clicked: cy.spy().as("onClickedSpy") } }
);

cy.get("counter-wc").shadow().as("shadow");

cy.get("@shadow").contains("h1", "Count is 42");
cy.get("@shadow").find("button").click();
cy.get("@onClickedSpy").should("have.been.calledWith", 42);
});
``

This enables passing spies and other overrides for testing purposes.

Contributing

- Open an issue or a PR with some comments to discuss the feat/fix