### Build and set up wasm-bindgen hello_world example

Source: https://github.com/vitest-dev/vitest/blob/main/test/unit/src/wasm/wasm-bindgen-no-cyclic/README.md

Installs dependencies, builds the project, and details the manual steps required to copy the package output and add module configuration to package.json.

```sh
npm i
npm run build
# then
# 1. copy `examples/hello_world/pkg` to this directory
# 2. add { "type": "module" } to `package.json`
#    (this will be automatically included after https://github.com/rustwasm/wasm-pack/pull/1061)
```

--------------------------------

### Run example tests with CI=true pnpm test:examples

Source: https://github.com/vitest-dev/vitest/blob/main/AGENTS.md

Runs the example tests in CI mode. Use to verify examples.

```bash
CI=true pnpm test:examples
```

--------------------------------

### Configure global setup with setupFiles

Source: https://github.com/vitest-dev/vitest/blob/main/docs/guide/learn/setup-teardown.md

Point `setupFiles` in `vitest.config.js` to a setup file like `test/setup.js` that runs before every test file. Use this for global setup such as polyfills and extending matchers with `expect.extend` before test collection begins.

```javascript
import { defineConfig } from 'vitest/config'

export default defineConfig({
  test: {
    setupFiles: ['./test/setup.js'],
  },
})
```

```javascript
// This runs before every test file
import { expect } from 'vitest'
import { customMatchers } from './custom-matchers.js'

expect.extend(customMatchers)
```

--------------------------------

### Define global setup and teardown using named exports

Source: https://github.com/vitest-dev/vitest/blob/main/docs/config/globalsetup.md

Export named `setup` and `teardown` functions in a global setup file. The `setup` function receives the `project` instance and runs before test workers are created.

```js
export function setup(project) {
  console.log('setup')
}

export function teardown() {
  console.log('teardown')
}
```

--------------------------------

### Configure Vitest to use a custom OpenTelemetry SDK

Source: https://github.com/vitest-dev/vitest/blob/main/docs/config/experimental.md

Example otel.js file that starts a NodeSDK instance and exports it as default. Use this as the sdkPath in Vitest configuration to enable OpenTelemetry.

```javascript
import { getNodeAutoInstrumentations } from '@opentelemetry/auto-instrumentations-node'
import { OTLPTraceExporter } from '@opentelemetry/exporter-trace-otlp-proto'
import { NodeSDK } from '@opentelemetry/sdk-node'

const sdk = new NodeSDK({
  serviceName: 'vitest',
  traceExporter: new OTLPTraceExporter(),
  instrumentations: [getNodeAutoInstrumentations()],
})

sdk.start()
export default sdk
```

```javascript
import { defineConfig } from 'vitest/config'

export default defineConfig({
  test: {
    experimental: {
      openTelemetry: {
        enabled: true,
        sdkPath: './otel.js',
      },
    },
  },
})
```

--------------------------------

### Generate HTML report and start UI dev server

Source: https://github.com/vitest-dev/vitest/blob/main/packages/ui/CONTRIBUTING.md

Generates an HTML report using the test:ui script and then starts the UI dev server pointing to the generated report directory. Use this as a complete example for HTML report development.

```bash
pnpm -C packages/ui test:ui --reporter=html --run
HTML_REPORT_DIR="$PWD/packages/ui/.vitest" pnpm -C packages/ui dev:client
```

--------------------------------

### Installing @vitest/browser-preview

Source: https://github.com/vitest-dev/vitest/blob/main/packages/browser-preview/README.md

Install the @vitest/browser-preview package as a development dependency using npm, yarn, or pnpm.

```sh
npm install -D @vitest/browser-preview
# or
yarn add -D @vitest/browser-preview
# or
pnpm add -D @vitest/browser-preview
```

--------------------------------

### Install dependencies with pnpm

Source: https://github.com/vitest-dev/vitest/blob/main/CONTRIBUTING.md

Run this command in the root folder of the Vitest repository to install all dependencies.

```shell
pnpm install
```

--------------------------------

### Install @vitest/ui package

Source: https://github.com/vitest-dev/vitest/blob/main/docs/guide/ui.md

Install Vitest UI as a development dependency.

```bash
npm i -D @vitest/ui
```

--------------------------------

### Providing context from a global setup file

Source: https://github.com/vitest-dev/vitest/blob/main/docs/api/advanced/test-project.md

Use provide within a global setup function when unable to use the Node.js public API directly.

```js
export default function setup({ provide }) {
  provide('wsPort', 3000)
}
```

--------------------------------

### Start Vitest with Live UI

Source: https://github.com/vitest-dev/vitest/blob/main/docs/guide/ui.md

Start Vitest in watch mode with the interactive UI enabled.

```bash
vitest --ui
```

--------------------------------

### Run setup and teardown with beforeEach return callback

Source: https://github.com/vitest-dev/vitest/blob/main/docs/api/hooks.md

Alternative to `aroundEach` when only simple pre-test setup and post-test cleanup are required without an enclosing context.

```typescript
beforeEach(async () => {
  await database.connect()
  return async () => {
    await database.disconnect()
  }
})
```

--------------------------------

### Install @vitest/web-worker

Source: https://github.com/vitest-dev/vitest/blob/main/packages/web-worker/README.md

Install the package as a development dependency using npm, pnpm, or yarn.

```bash
# with npm
npm install -D @vitest/web-worker

# with pnpm
pnpm install -D @vitest/web-worker

# with yarn
yarn add --dev @vitest/web-worker
```

--------------------------------

### Example DOM structure for query and element

Source: https://github.com/vitest-dev/vitest/blob/main/docs/api/browser/locators.md

HTML structure used in the query and element examples.

```html
<div>Hello <span>World</span></div>
<div>Hello</div>
```

--------------------------------

### Install OpenTelemetry browser tracing dependencies

Source: https://github.com/vitest-dev/vitest/blob/main/docs/guide/open-telemetry.md

Installs the web trace SDK and OTLP proto exporter required for capturing traces in browser mode.

```shell
npm i @opentelemetry/sdk-trace-web @opentelemetry/exporter-trace-otlp-proto
```

--------------------------------

### Install @chromatic-com/vitest plugin

Source: https://github.com/vitest-dev/vitest/blob/main/docs/guide/browser/visual-regression-testing.md

Install the Chromatic Vitest plugin using your package manager of choice as a development dependency.

```bash
npm install -D @chromatic-com/vitest
```

```bash
yarn add -D @chromatic-com/vitest
```

```bash
pnpm add -D @chromatic-com/vitest
```

--------------------------------

### Install Vitest using bun

Source: https://github.com/vitest-dev/vitest/blob/main/docs/guide/index.md

Installs Vitest as a development dependency using bun. Vitest requires Vite >=v6.4.0 and Node >=v22.12.0.

```bash
bun add -D vitest
```

--------------------------------

### Manually install Vitest with WebdriverIO provider

Source: https://github.com/vitest-dev/vitest/blob/main/docs/guide/browser/index.md

Installs Vitest and the WebdriverIO provider. WebdriverIO runs tests locally using the WebDriver protocol.

```bash
npm install -D vitest @vitest/browser-webdriverio
```

```bash
yarn add -D vitest vite @vitest/browser-webdriverio
```

```bash
pnpm add -D vitest @vitest/browser-webdriverio
```

```bash
bun add -D vitest @vitest/browser-webdriverio
```

--------------------------------

### vi.resetModules usage example

Source: https://github.com/vitest-dev/vitest/blob/main/docs/api/vi.md

Example showing that vi.resetModules clears the module cache so dynamic imports get fresh state, while top-level imports are not reevaluated.

```ts
import { vi } from 'vitest'

import { data } from './data.js' // Will not get reevaluated beforeEach test

beforeEach(() => {
  vi.resetModules()
})

test('change state', async () => {
  const mod = await import('./some/path.js') // Will get reevaluated
  mod.changeLocalState('new value')
  expect(mod.getLocalState()).toBe('new value')
})

test('module has old state', async () => {
  const mod = await import('./some/path.js') // Will get reevaluated
  expect(mod.getLocalState()).toBe('old value')
})
```

--------------------------------

### Configure and test different instance setups with provide and setupFiles

Source: https://github.com/vitest-dev/vitest/blob/main/docs/guide/browser/multiple-setups.md

Defines multiple instance setups using custom names, setupFiles, and provide values, and consumes the injected values within a test file.

```ts
import { defineConfig } from 'vitest/config'
import { playwright } from '@vitest/browser-playwright'

export default defineConfig({
  test: {
    browser: {
      enabled: true,
      provider: playwright(),
      headless: true,
      instances: [
        { precedence: undefined, browser: 'chromium', name: 'chromium-1', setupFiles: ['./ratio-setup.ts'], provide: { ratio: 1 } } as any ? {
          browser: 'chromium',
          name: 'chromium-1',
          setupFiles: ['./ratio-setup.ts'],
          provide: {
            ratio: 1,
          },
        } : null,
        {
          browser: 'chromium',
          name: 'chromium-2',
          provide: {
            ratio: 2,
          },
        },
      ],
    },
  },
})
```

```ts
import { expect, inject, test } from 'vitest'
import { globalSetupModifier } from './example.js'

test('ratio works', () => {
  expect(inject('ratio') * globalSetupModifier).toBe(14)
})
```

--------------------------------

### createVitest(options, viteOverrides?, vitestOptions?)

Source: https://github.com/vitest-dev/vitest/blob/main/docs/guide/advanced/index.md

Creates a Vitest instance without automatically starting tests or validating installed packages. It returns the same Vitest instance as startVitest.

```APIDOC
## createVitest

### Description
Creates a Vitest instance using the provided options. Returns the same `Vitest` instance as `startVitest`, but does not start tests or validate installed packages.

### Function Signature
```ts
function createVitest(
  options: CliOptions,
  viteOverrides: ViteUserConfig = {},
  vitestOptions: VitestOptions = {},
): Promise<Vitest>
```

### Parameters
- **options** (`CliOptions`) - Required - Vitest CLI options.
- **viteOverrides** (`ViteUserConfig`) - Optional - Overrides for Vite configuration. Defaults to `{}`.
- **vitestOptions** (`VitestOptions`) - Optional - Additional Vitest options. Defaults to `{}`.

### Returns
- `Promise<Vitest>` - A promise that resolves to a `Vitest` instance.

### Example
```js
import { createVitest } from 'vitest/node'

const vitest = await createVitest('test', {
  watch: false,
})
```
```

--------------------------------

### Run setup and teardown once using beforeAll cleanup function

Source: https://github.com/vitest-dev/vitest/blob/main/docs/api/hooks.md

Demonstrates the preferred alternative to aroundAll when only simple setup and teardown are needed rather than an active wrapper context.

```typescript
beforeAll(async () => {
  await server.start()
  return async () => {
    await server.stop()
  }
})
```

--------------------------------

### Initialize browser setup with vitest init

Source: https://github.com/vitest-dev/vitest/blob/main/docs/guide/cli.md

`vitest init <name>` sets up project configuration. Currently only the `browser` value is supported.

```bash
vitest init browser
```

--------------------------------

### Define createVitest Type Signature

Source: https://github.com/vitest-dev/vitest/blob/main/docs/guide/advanced/index.md

Type definition for createVitest, returning a Promise that resolves to a Vitest instance without starting tests or validating installed packages.

```typescript
function createVitest(
  options: CliOptions,
  viteOverrides: ViteUserConfig = {},
  vitestOptions: VitestOptions = {},
): Promise<Vitest>
```

--------------------------------

### startVitest(cliFilters, testConfig, viteConfig, vitestOptions)

Source: https://github.com/vitest-dev/vitest/blob/main/docs/guide/advanced/tests.md

Initiates Vitest, validates that required packages are installed, and runs tests immediately. It returns the active Vitest instance.

```APIDOC
## startVitest

### Description
Initiates Vitest, validates that required packages are installed, and immediately executes the test suite.

### Signature
`startVitest(cliFilters?, testConfig?, viteConfig?, vitestOptions?): Promise<Vitest>`

### Parameters
- **cliFilters** (`string[]`) - Optional - Array of CLI filter patterns to filter tests to execute.
- **testConfig** (`Record<string, any>`) - Optional - Configuration object overriding Vitest test options.
- **viteConfig** (`Record<string, any>`) - Optional - Configuration object overriding Vite options.
- **vitestOptions** (`Record<string, any>`) - Optional - Custom Vitest CLI/node options.

### Usage Example
```ts
import { startVitest } from 'vitest/node'

const vitest = await startVitest(
  [], // CLI filters
  {}, // override test config
  {}, // override Vite config
  {}, // custom Vitest options
)
const testModules = vitest.state.getTestModules()
for (const testModule of testModules) {
  console.log(testModule.moduleId, testModule.ok() ? 'passed' : 'failed')
}
```
```

--------------------------------

### toHaveBeenNthCalledWith checks specific call arguments

Source: https://github.com/vitest-dev/vitest/blob/main/docs/api/expect.md

Use with a spy to assert the arguments of a specific call, where the count starts at 1. The example verifies the first call to market.buy used 'apples', 10.

```ts
import { expect, test, vi } from 'vitest'

const market = {
  buy(subject: string, amount: number) {
    // ...
  },
}

test('first call of spy function called with right params', () => {
  const buySpy = vi.spyOn(market, 'buy')

  market.buy('apples', 10)
  market.buy('apples', 20)

  expect(buySpy).toHaveBeenNthCalledWith(1, 'apples', 10)
})
```

--------------------------------

### Perform one-time setup and teardown with beforeAll and afterAll

Source: https://github.com/vitest-dev/vitest/blob/main/docs/guide/learn/setup-teardown.md

Use beforeAll and afterAll to execute expensive operations once for an entire test file. Shared resources like database connections are created once, accessed across all file tests, and closed upon completion.

```javascript
import { afterAll, beforeAll, expect, test } from 'vitest'

let db

beforeAll(async () => {
  db = await connectToDatabase()
})

afterAll(async () => {
  await db.close()
})

test('can query users', async () => {
  const users = await db.query('SELECT * FROM users')
  expect(users.length).toBeGreaterThan(0)
})

test('can query products', async () => {
  const products = await db.query('SELECT * FROM products')
  expect(products.length).toBeGreaterThan(0)
})
```

--------------------------------

### Run Playwright Server in Docker and connect via connectOptions

Source: https://github.com/vitest-dev/vitest/blob/main/docs/config/browser/playwright.md

Defines a Docker Compose setup to run a remote Playwright server, starts the container, and configures Vitest to connect via WebSocket. Uses `exposeNetwork: '<loopback>'` to allow containerized browsers to access the host dev server.

```yaml
services:
  playwright:
    image: mcr.microsoft.com/playwright:v1.61.0-noble
    command: /bin/sh -c "npx -y playwright@1.61.0 run-server --port 6677 --host 0.0.0.0"
    init: true
    ipc: host
    user: pwuser
    ports:
      - '6677:6677'
```

```sh
docker compose up -d
```

```ts
import { playwright } from '@vitest/browser-playwright'
import { defineConfig } from 'vitest/config'

export default defineConfig({
  test: {
    browser: {
      provider: playwright({
        connectOptions: {
          wsEndpoint: 'ws://127.0.0.1:6677/',
          exposeNetwork: '<loopback>',
        },
      }),
      instances: [
        { browser: 'chromium' },
        { browser: 'firefox' },
        { browser: 'webkit' },
      ],
    },
  },
})
```

--------------------------------

### Start Vitest UI with token authentication

Source: https://github.com/vitest-dev/vitest/blob/main/docs/guide/migration/index.md

Run vitest --ui to start the UI. The printed URL includes a token; open it to authenticate, after which the direct /__vitest__/ URL works.

```bash
vitest --ui
# UI started at http://localhost:51204/__vitest__/?token=...
```

--------------------------------

### userEvent.setup

Source: https://github.com/vitest-dev/vitest/blob/main/docs/api/browser/interactivity.md

Creates a new user event instance. This is useful if you need to keep the state of keyboard to press and release buttons correctly.

```APIDOC
## userEvent.setup

### Description
Creates a new user event instance. This is useful if you need to keep the state of keyboard to press and release buttons correctly.

### Method
`setup()`

### Parameters
None.

### Returns
- **UserEvent** - A new user event instance.

### Example
```ts
import { userEvent } from 'vitest/browser'

const user = userEvent.setup()
await user.click(document.querySelector('.button'))
```
```

--------------------------------

### Execute setup logic before each test with beforeEach

Source: https://github.com/vitest-dev/vitest/blob/main/docs/api/hooks.md

Registers an asynchronous setup function that runs prior to every test in the suite. Vitest waits for returned promises to resolve before test execution.

```ts
import { beforeEach } from 'vitest'

beforeEach(async () => {
  // Clear mocks and add some testing data before each test run
  await stopMocking()
  await addUser({ name: 'John' })
})
```

--------------------------------

### Example DOM structure for element

Source: https://github.com/vitest-dev/vitest/blob/main/docs/api/browser/locators.md

HTML structure used in the element examples.

```html
<div>Hello <span>World</span></div>
<div>Hello Germany</div>
<div>Hello</div>
```

--------------------------------

### Preview HTML report locally with vite preview

Source: https://github.com/vitest-dev/vitest/blob/main/docs/guide/ui.md

Start a local preview server serving the default .vitest output directory.

```sh
npx vite preview --outDir .vitest
```

--------------------------------

### vi.advanceTimersToNextFrame Example

Source: https://github.com/vitest-dev/vitest/blob/main/docs/api/vi.md

Example showing vi.advanceTimersToNextFrame triggering a requestAnimationFrame callback and asserting it ran.

```ts
let frameRendered = false

requestAnimationFrame(() => {
  frameRendered = true
})

vi.advanceTimersToNextFrame()

expect(frameRendered).toBe(true)
```

--------------------------------

### toBeDisabled example HTML

Source: https://github.com/vitest-dev/vitest/blob/main/docs/api/browser/assertions.md

HTML markup for a disabled button used in the toBeDisabled example.

```html
<button
  data-testid="button"
  type="submit"
  disabled
>
  submit
</button>
```

--------------------------------

### Manually install Vitest with preview provider

Source: https://github.com/vitest-dev/vitest/blob/main/docs/guide/browser/index.md

Installs Vitest and the preview provider for local test preview. The preview provider simulates events and is not recommended for CI; use Playwright or WebdriverIO for CI.

```bash
npm install -D vitest @vitest/browser-preview
```

```bash
yarn add -D vitest vite @vitest/browser-preview
```

```bash
pnpm add -D vitest @vitest/browser-preview
```

```bash
bun add -D vitest @vitest/browser-preview
```

--------------------------------

### Configure browser.instances with inherited root config options

Source: https://github.com/vitest-dev/vitest/blob/main/docs/config/browser/instances.md

Demonstrates how browser instance configurations inherit options from the root config, such as setup files and testerHtmlPath.

```ts
export default defineConfig({
  test: {
    setupFile: ['./root-setup-file.js'],
    browser: {
      enabled: true,
      testerHtmlPath: './custom-path.html',
      instances: [
        {
          // will have both setup files: "root" and "browser"
          setupFile: ['./browser-setup-file.js'],
          // implicitly has "testerHtmlPath" from the root config // [!code warning]
          // testerHtmlPath: './custom-path.html', // [!code warning]
        },
      ],
    },
  },
})
```

--------------------------------

### screenshot method TypeScript signatures

Source: https://github.com/vitest-dev/vitest/blob/main/docs/api/browser/locators.md

TypeScript overloads for the screenshot method. Use save: false to get a base64 string, base64: true to get both path and base64, or default to get only the file path.

```typescript
function screenshot(options: LocatorScreenshotOptions & { save: false }): Promise<string>
function screenshot(options: LocatorScreenshotOptions & { base64: true }): Promise<{
  path: string
  base64: string
}>
function screenshot(options?: LocatorScreenshotOptions & { base64?: false }): Promise<string>
```

--------------------------------

### Initialize Browser Mode with vitest init browser

Source: https://github.com/vitest-dev/vitest/blob/main/docs/guide/browser/index.md

Automatically installs required dependencies and creates browser configuration. Run this command in your project root.

```bash
npx vitest init browser
```

```bash
yarn exec vitest init browser
```

```bash
pnpx vitest init browser
```

```bash
bunx vitest init browser
```

--------------------------------

### vi.runOnlyPendingTimers Example

Source: https://github.com/vitest-dev/vitest/blob/main/docs/api/vi.md

Example showing vi.runOnlyPendingTimers executing only the pending interval timer once, logging 1.

```ts
let i = 0
setInterval(() => console.log(++i), 50)

vi.runOnlyPendingTimers()

// log: 1
```

--------------------------------

### vi.runAllTimersAsync Example

Source: https://github.com/vitest-dev/vitest/blob/main/docs/api/vi.md

Example showing await vi.runAllTimersAsync executing an asynchronous setTimeout that logs 'result'.

```ts
setTimeout(async () => {
  console.log(await Promise.resolve('result'))
}, 100)

await vi.runAllTimersAsync()

// log: result
```

--------------------------------

### Define a sample class with fields and prototype methods

Source: https://github.com/vitest-dev/vitest/blob/main/docs/guide/mocking/classes.md

Demonstrates a class with both instance fields (greet) and prototype methods (speak, isHungry, and feed) to illustrate differences in mock behavior.

```ts
class Dog {
  name: string

  constructor(name: string) {
    this.name = name
  }

  static getType(): string {
    return 'animal'
  }

  greet = (): string => {
    return `Hi! My name is ${this.name}!`
  }

  speak(): string {
    return 'bark!'
  }

  isHungry() {}
  feed() {}
}
```

--------------------------------

### Start Vitest UI/API server for test/unit

Source: https://github.com/vitest-dev/vitest/blob/main/packages/ui/CONTRIBUTING.md

Runs the test/unit suite with UI enabled to serve as the backend for the UI dev server. Use from the repository root.

```bash
pnpm test --ui --open=false
```

--------------------------------

### start

Source: https://github.com/vitest-dev/vitest/blob/main/docs/api/advanced/vitest.md

Initializes reporters, the coverage provider, and runs tests. Accepts string filters to match test files, similar to CLI filters. Should not be called if standalone() is also invoked; use runTestSpecifications or rerunTestSpecifications instead for running tests after initialization.

```APIDOC
## start

### Description
Initialize reporters, the coverage provider, and run tests. This method accepts string filters to match the test files - these are the same filters that CLI supports.

::: warning
This method should not be called if `vitest.standalone()` is also invoked. Use `runTestSpecifications` or `rerunTestSpecifications` instead if you need to run tests after Vitest was initialised.
:::

This method is called automatically by `startVitest` if `config.mergeReports` and `config.standalone` are not set.

### Method
`start`

### Parameters
- **filters** (string[]) - Optional - String filters to match test files.

### Returns
`Promise<TestRunResult>`

### Example
```ts
const result = await vitest.start(['**/*.test.ts']);
```
```

--------------------------------

### toHaveFormValues usage example

Source: https://github.com/vitest-dev/vitest/blob/main/docs/api/browser/assertions.md

TypeScript example asserting that a form has specific values for username and rememberMe fields.

```typescript
await expect.element(getByTestId('login-form')).toHaveFormValues({
  username: 'jane.doe',
  rememberMe: true,
})
```

--------------------------------

### Configure per-file setup and global hooks in setup files

Source: https://github.com/vitest-dev/vitest/blob/main/docs/guide/lifecycle.md

Runs in the worker process before each test file executes. Use this file to initialize global state or register hooks that apply to all tests.

```ts
import { afterEach } from 'vitest'

// Runs before each test file
console.log('Setup file executing')

// Register hooks that apply to all tests
afterEach(() => {
  cleanup()
})
```

--------------------------------

### toContainHTML HTML Example

Source: https://github.com/vitest-dev/vitest/blob/main/docs/api/browser/assertions.md

HTML structure used in the toContainHTML example, showing a parent and child element.

```html
<span data-testid="parent"><span data-testid="child"></span></span>
```

--------------------------------

### Initiate and run tests with startVitest

Source: https://github.com/vitest-dev/vitest/blob/main/docs/guide/advanced/tests.md

Uses `startVitest` to initiate Vitest, validate dependencies, run tests immediately, and inspect test module results.

```ts
import { startVitest } from 'vitest/node'

const vitest = await startVitest(
  [], // CLI filters
  {}, // override test config
  {}, // override Vite config
  {}, // custom Vitest options
)
const testModules = vitest.state.getTestModules()
for (const testModule of testModules) {
  console.log(testModule.moduleId, testModule.ok() ? 'passed' : 'failed')
}
```

--------------------------------

### toContainElement HTML Example

Source: https://github.com/vitest-dev/vitest/blob/main/docs/api/browser/assertions.md

HTML structure used in the toContainElement example, showing an ancestor and descendant element.

```html
<span data-testid="ancestor"><span data-testid="descendant"></span></span>
```

--------------------------------

### Set up Chromatic GitHub Action workflow in .github/workflows/chromatic.yml

Source: https://github.com/vitest-dev/vitest/blob/main/docs/guide/browser/visual-regression-testing.md

Automate running Vitest and uploading snapshots to Chromatic within GitHub Actions using chromaui/action.

```yaml
name: Chromatic

on: push

jobs:
  tests:
    name: Run Vitest & Chromatic
    runs-on: ubuntu-latest
    steps:
      - name: Checkout code
        uses: actions/checkout@v7

      - uses: actions/setup-node@v7
        with:
          node-version: 24

      # ⚠️ See your package manager's documentation for the correct command to install dependencies in a CI environment.
      - name: Install dependencies
        run: npm ci

      - run: npx playwright install chromium --only-shell

      - name: Run Vitest tests
        run: npm run test

      - name: Run Chromatic
        uses: chromaui/action@latest
        with:
          # ⚠️ Enable Vitest
          vitest: true
          # ⚠️ Make sure to configure a `CHROMATIC_PROJECT_TOKEN` repository secret
          projectToken: ${{ secrets.CHROMATIC_PROJECT_TOKEN }}
        # ⚠️ Optionally configure the archive location with env vars to match your outputDirectory https://www.chromatic.com/docs/vitest/configure/#test-run-options
        env:
          CHROMATIC_ARCHIVE_LOCATION: .vitest/chromatic
```

--------------------------------

### toBeEmptyDOMElement example HTML

Source: https://github.com/vitest-dev/vitest/blob/main/docs/api/browser/assertions.md

HTML markup with empty, whitespace, and comment elements used in the toBeEmptyDOMElement example.

```html
<span data-testid="not-empty"><span data-testid="empty"></span></span>
<span data-testid="with-whitespace"> </span>
<span data-testid="with-comment"><!-- comment --></span>
```

--------------------------------

### startVitest(cliFilters, options, viteOverrides, vitestOptions)

Source: https://github.com/vitest-dev/vitest/blob/main/docs/guide/advanced/index.md

Programmatically starts running Vitest tests using its Node.js API. Returns a Vitest instance if tests can be started.

```APIDOC
## startVitest

### Description
Starts running Vitest tests using its Node API. If watch mode is not enabled, Vitest calls the `close` method automatically. If watch mode is enabled and the terminal supports TTY, it registers console shortcuts.

### Import
```ts
import { startVitest } from 'vitest/node'
```

### Signature
```ts
function startVitest(
  cliFilters: string[] = [],
  options: CliOptions = {},
  viteOverrides?: ViteUserConfig,
  vitestOptions?: VitestOptions,
): Promise<Vitest>
```

### Parameters
- **cliFilters** (`string[]`) - Optional (default: `[]`) - List of filters. Vitest will run only tests that contain at least one of the passed-down strings in their file path.
- **options** (`CliOptions`) - Optional (default: `{}`) - CLI arguments overriding test config options.
- **viteOverrides** (`ViteUserConfig`) - Optional - Complete Vite configuration taking precedence over other user-defined options.
- **vitestOptions** (`VitestOptions`) - Optional - Vitest configuration options.

### Return Value
- **Promise<Vitest>** - Returns a `Promise` resolving to a `Vitest` instance if tests can be started.

### Usage Example
```js
import { startVitest } from 'vitest/node'

const vitest = await startVitest()

console.log(vitest.state.getTestModules())

await vitest.close()
```
```

--------------------------------

### Static meta example

Source: https://github.com/vitest-dev/vitest/blob/main/docs/api/advanced/test-case.md

Shows how to define static meta when creating a test, which is available even if the test has not finished running.

```ts
test('the validation works correctly', { meta: { decorated: true } })
```

--------------------------------

### vi.advanceTimersByTime Example

Source: https://github.com/vitest-dev/vitest/blob/main/docs/api/vi.md

Example showing vi.advanceTimersByTime advancing an interval timer by 150ms, logging 1, 2, and 3.

```ts
let i = 0
setInterval(() => console.log(++i), 50)

vi.advanceTimersByTime(150)

// log: 1
// log: 2
// log: 3
```

--------------------------------

### toHaveFocus usage example

Source: https://github.com/vitest-dev/vitest/blob/main/docs/api/browser/assertions.md

TypeScript example showing how to focus and blur an input and assert focus state with toHaveFocus.

```typescript
const input = page.getByTestId('element-to-focus')
input.element().focus()
await expect.element(input).toHaveFocus()
input.element().blur()
await expect.element(input).not.toHaveFocus()
```

--------------------------------

### Example module for vi.doMock

Source: https://github.com/vitest-dev/vitest/blob/main/docs/api/vi.md

A simple increment function used to demonstrate vi.doMock behavior.

```ts
export function increment(number) {
  return number + 1
}
```

--------------------------------

### vi.importActual usage example

Source: https://github.com/vitest-dev/vitest/blob/main/docs/api/vi.md

Example of using vi.importActual to import the original module and then override a specific export with a mock.

```ts
vi.mock('./example.js', async () => {
  const originalModule = await vi.importActual('./example.js')

  return { ...originalModule, get: vi.fn() }
})
```

--------------------------------

### Installing @vitest/browser-playwright

Source: https://github.com/vitest-dev/vitest/blob/main/packages/browser-playwright/README.md

Install the Playwright browser provider package as a development dependency using npm, yarn, or pnpm.

```sh
npm install -D @vitest/browser-playwright
# or
yarn add -D @vitest/browser-playwright
# or
pnpm add -D @vitest/browser-playwright
```