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Best Practices for Testing React Components using Vitest and Jest

Before writing tests, ensure your project has the necessary dependencies:

Terminal window
npm install --save-dev vitest jsdom @testing-library/dom @testing-library/jest-dom @testing-library/react @testing-library/user-event

Configuration

Create the vite.config.ts file to configure Vitest.

import { defineConfig } from "vitest/config"


export default defineConfig({
  // ...
  test: {
    globals: true,
    environment: "jsdom",
    setupFiles: "./setup-test.ts",
  },
})

Setting globals: true will automatically import the Vitest globals and removes the need to import expect, test, describe, etc.

Setup Test File

Create the setup-test.ts file to configure the testing environment and mock unimplemented APIs.

Here's a common example for Cerberus projects:

setup-test.ts
import "@testing-library/jest-dom/vitest"
import { JSDOM } from "jsdom"
import ResizeObserver from "resize-observer-polyfill"
import { vi } from "vitest"
import "vitest-axe/extend-expect"


const { window } = new JSDOM()


// ResizeObserver mock
vi.stubGlobal("ResizeObserver", ResizeObserver)
window["ResizeObserver"] = ResizeObserver


// IntersectionObserver mock
const IntersectionObserverMock = vi.fn(() => ({
  disconnect: vi.fn(),
  observe: vi.fn(),
  takeRecords: vi.fn(),
  unobserve: vi.fn(),
}))
vi.stubGlobal("IntersectionObserver", IntersectionObserverMock)
window["IntersectionObserver"] = IntersectionObserverMock


// Scroll Methods mock
window.Element.prototype.scrollTo = () => {}
window.Element.prototype.scrollIntoView = () => {}


// requestAnimationFrame mock
window.requestAnimationFrame = (cb) => setTimeout(cb, 1000 / 60)


// URL object mock
window.URL.createObjectURL = () => "https://i.pravatar.cc/300"
window.URL.revokeObjectURL = () => {}


// navigator mock
Object.defineProperty(window, "navigator", {
  value: {
    clipboard: {
      writeText: vi.fn(),
    },
  },
})


// Override globalThis
Object.assign(global, { window, document: window.document })

Custom Render

First, you need to create a custom render function to wrap your component in the CerberusProvider.

test-utils/render.tsx
import { render as rtlRender } from "@testing-library/react"
import {
  CerberusProvider,
  defineIcons,
  makeSystemConfig,
  NotificationCenter,
} from '@cerberus/react'


const config = makeSystemConfig({
  icons: defineIcons({
    // Define your icons here
    // Example: "home": <svg>...</svg>
  }),
})


export function render(ui: ReactNode) {
  return rtlRender(<>{ui}</>, {
    wrapper: (props: PropsWithChildren) => (
      <CerberusProvider config={config}>
        {props.children}
        <NotificationCenter />
      </CerberusProvider>
    ),
  })
}

Testing Components

Now, you can use the render function to test your components.

testing/render.tsx
import { Button } from "@cerberus/react"
import { render } from "./testing/render"


test("renders a button", () => {
  render(<Button>Click me</Button>)
  expect(screen.getByText("Click me")).toBeInTheDocument()
})

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