Running cypress component testing on web components and lit elements.
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npm i -D cypress-lit
yarn add -D cypress-lit
pnpm i -D cypress-lit
The command needs to be imported from the package and added to cypress commands.
# ./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.
// ./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,
});
There is a collection of tests for:
You can pass a hit template directly to the mount command.
// ./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`<counter-lit></counter-lit>`);
cy.get("counter-lit").shadow().contains("h1", "Count is 0");
});
If you have custom elements defined using pure browser javascript then you can pass in a string.
// ./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">(`<counter-wc></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:
// ./cypress/component/web-component.cy.ts#L26-L39
it("can pass emitters as spies", () => {
cy.mount<"counter-wc">(
`<counter-wc
count=${42}
></counter-wc>`,
{ 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.
Open an issue or a PR with some comments to discuss the feat/fix.
For local running you should be set with:
pnpm i
pnpm lint
pnpm build
pnpm test