Vi

Vitest provides utility functions to help you out through its vi helper. You can access it globally (when globals configuration is enabled), or import from vitest:

import { vi } from 'vitest'

vi.advanceTimersByTime

Type: (ms: number) => Vitest

Works just like runAllTimers, but will end after passed milliseconds. For example this will log 1, 2, 3 and will not throw:
```
let i = 0
setInterval(() => console.log(++i), 50)

vi.advanceTimersByTime(150)
```

vi.advanceTimersByTimeAsync

Type: (ms: number) => Promise<Vitest>

Works just like runAllTimersAsync, but will end after passed milliseconds. This will include asynchronously set timers. For example this will log 1, 2, 3 and will not throw:
```
let i = 0
setInterval(() => Promise.resolve().then(() => console.log(++i)), 50)

await vi.advanceTimersByTimeAsync(150)
```

vi.advanceTimersToNextTimer

Type: () => Vitest

Will call next available timer. Useful to make assertions between each timer call. You can chain call it to manage timers by yourself.

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

vi.advanceTimersToNextTimer() // log 1
  .advanceTimersToNextTimer() // log 2
  .advanceTimersToNextTimer() // log 3

vi.advanceTimersToNextTimerAsync

Type: () => Promise<Vitest>

Will call next available timer even if it was set asynchronously. Useful to make assertions between each timer call. You can chain call it to manage timers by yourself.

let i = 0
setInterval(() => Promise.resolve().then(() => console.log(++i)), 50)

vi.advanceTimersToNextTimerAsync() // log 1
  .advanceTimersToNextTimerAsync() // log 2
  .advanceTimersToNextTimerAsync() // log 3

vi.getTimerCount

Type: () => number

Get the number of waiting timers.

vi.clearAllMocks

Will call .mockClear() on all spies. This will clear mock history, but not reset its implementation to the default one.

vi.clearAllTimers

Removes all timers that are scheduled to run. These timers will never run in the future.

vi.dynamicImportSettled

Wait for all imports to load. Useful, if you have a synchronous call that starts importing a module, that you cannot wait otherwise.

vi.fn

Type: (fn?: Function) => CallableMockInstance

Creates a spy on a function, though can be initiated without one. Every time a function is invoked, it stores its call arguments, returns, and instances. Also, you can manipulate its behavior with methods. If no function is given, mock will return undefined, when invoked.
```
const getApples = vi.fn(() => 0)

getApples()

expect(getApples).toHaveBeenCalled()
expect(getApples).toHaveReturnedWith(0)

getApples.mockReturnValueOnce(5)

const res = getApples()
expect(res).toBe(5)
expect(getApples).toHaveNthReturnedWith(2, 5)
```

vi.getMockedSystemTime

Type: () => Date | null

Returns mocked current date that was set using setSystemTime. If date is not mocked, will return null.

vi.getRealSystemTime

Type: () => number

When using vi.useFakeTimers, Date.now calls are mocked. If you need to get real time in milliseconds, you can call this function.

vi.mock

Type: (path: string, factory?: () => unknown) => void

Substitutes all imported modules from provided path with another module. You can use configured Vite aliases inside a path. The call to vi.mock is hoisted, so it doesn't matter where you call it. It will always be executed before all imports.

::: warning vi.mock works only for modules that were imported with the import keyword. It doesn't work with require.

Vitest statically analyzes your files to hoist vi.mock. It means that you cannot use vi that was not imported directly from vitest package (for example, from some utility file). To fix this, always use vi.mock with vi imported from vitest, or enable globals config option. :::

If factory is defined, all imports will return its result. Vitest calls factory only once and caches result for all subsequent imports until vi.unmock or vi.doUnmock is called.

Unlike in jest, the factory can be asynchronous, so you can use vi.importActual or a helper, received as the first argument, inside to get the original module.
```
vi.mock('./path/to/module.js', async (importOriginal) => {
  const mod = await importOriginal()
  return {
    ...mod,
    // replace some exports
    namedExport: vi.fn(),
  }
})
```
::: warning vi.mock is hoisted (in other words, moved) to top of the file. It means that whenever you write it (be it inside beforeEach or test), it will actually be called before that.

This also means that you cannot use any variables inside the factory that are defined outside the factory.

If you need to use variables inside the factory, try vi.doMock. It works the same way but isn't hoisted. Beware that it only mocks subsequent imports. :::

::: warning If you are mocking a module with default export, you will need to provide a default key within the returned factory function object. This is an ES modules-specific caveat, therefore jest documentation may differ as jest uses CommonJS modules. For example,
```
vi.mock('./path/to/module.js', () => {
  return {
    default: { myDefaultKey: vi.fn() },
    namedExport: vi.fn(),
    // etc...
  }
})
```
:::

If there is a __mocks__ folder alongside a file that you are mocking, and the factory is not provided, Vitest will try to find a file with the same name in the __mocks__ subfolder and use it as an actual module. If you are mocking a dependency, Vitest will try to find a __mocks__ folder in the root of the project (default is process.cwd()).

For example, you have this file structure:
```
- __mocks__
  - axios.js
- src
  __mocks__
    - increment.js
  - increment.js
- tests
  - increment.test.js
```
If you call vi.mock in a test file without a factory provided, it will find a file in the __mocks__ folder to use as a module:
```
// increment.test.js
import { vi } from 'vitest'
// axios is a default export from `__mocks__/axios.js`
import axios from 'axios'
// increment is a named export from `src/__mocks__/increment.js`
import { increment } from '../increment.js'

vi.mock('axios')
vi.mock('../increment.js')

axios.get(`/apples/${increment(1)}`)
```
::: warning Beware that if you don't call vi.mock, modules are not mocked automatically. :::

If there is no __mocks__ folder or a factory provided, Vitest will import the original module and auto-mock all its exports. For the rules applied, see algorithm.

vi.doMock

Type: (path: string, factory?: () => unknown) => void

The same as vi.mock, but it's not hoisted at the top of the file, so you can reference variables in the global file scope. The next import of the module will be mocked. This will not mock modules that were imported before this was called.

// ./increment.js
export const increment = number => number + 1

import { beforeEach, test } from 'vitest'
import { increment } from './increment.js'

// the module is not mocked, because vi.doMock is not called yet
increment(1) === 2

let mockedIncrement = 100

beforeEach(() => {
  // simple doMock doesn't clear the previous cache, so we need to clear it manually here
  vi.doUnmock('./increment.js')
  // you can access variables inside a factory
  vi.doMock('./increment.js', () => ({ increment: () => mockedIncrement++ }))
})

test('importing the next module imports mocked one', () => {
  // original import WAS NOT MOCKED, because vi.doMock is evaluated AFTER imports
  expect(increment(1)).toBe(2)
  const { increment: mockedIncrement } = await import('./increment.js')
  // new import returns mocked module
  expect(mockedIncrement(1)).toBe(101)
  expect(mockedIncrement(1)).toBe(102)
  expect(mockedIncrement(1)).toBe(103)
})

vi.mocked

Type: <T>(obj: T, deep?: boolean) => MaybeMockedDeep<T>
Type: <T>(obj: T, options?: { partial?: boolean; deep?: boolean }) => MaybePartiallyMockedDeep<T>

Type helper for TypeScript. In reality just returns the object that was passed.

When partial is true it will expect a Partial<T> as a return value.
```
import example from './example'
vi.mock('./example')

test('1+1 equals 2', async () => {
  vi.mocked(example.calc).mockRestore()

  const res = example.calc(1, '+', 1)

  expect(res).toBe(2)
})
```

vi.importActual

Type: <T>(path: string) => Promise<T>

Imports module, bypassing all checks if it should be mocked. Can be useful if you want to mock module partially.
```
vi.mock('./example', async () => {
  const axios = await vi.importActual('./example')

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

vi.importMock

Type: <T>(path: string) => Promise<MaybeMockedDeep<T>>

Imports a module with all of its properties (including nested properties) mocked. Follows the same rules that vi.mock follows. For the rules applied, see algorithm.

vi.resetAllMocks

Will call .mockReset() on all spies. This will clear mock history and reset its implementation to an empty function (will return undefined).

vi.resetConfig

Type: RuntimeConfig

If vi.setConfig was called before, this will reset config to the original state.

vi.resetModules

Type: () => Vitest

Resets modules registry by clearing cache of all modules. Might be useful to isolate modules where local state conflicts between tests.

import { vi } from 'vitest'

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

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

test('module has old state', async () => {
  const mod = await import('./some/path')
  expect(mod.getlocalState()).toBe('old value')
})

::: warning Does not reset mocks registry. To clear mocks registry, use vi.unmock or vi.doUnmock. :::

vi.restoreAllMocks

Will call .mockRestore() on all spies. This will clear mock history and reset its implementation to the original one.

vi.restoreCurrentDate

Type: () => void

Restores Date back to its native implementation.

vi.stubEnv

Type: (name: string, value: string) => Vitest
Version: Since Vitest 0.26.0

Changes the value of environmental variable on process.env and import.meta.env. You can restore its value by calling vi.unstubAllEnvs.

import { vi } from 'vitest'

// `process.env.NODE_ENV` and `import.meta.env.NODE_ENV`
// are "development" before calling "vi.stubEnv"

vi.stubEnv('NODE_ENV', 'production')

process.env.NODE_ENV === 'production'
import.meta.env.NODE_ENV === 'production'
// doesn't change other envs
import.meta.env.MODE === 'development'

:::tip You can also change the value by simply assigning it, but you won't be able to use vi.unstubAllEnvs to restore previous value:

import.meta.env.MODE = 'test'

:::

:::warning Vitest transforms all import.meta.env calls into process.env, so they can be easily changed at runtime. Node.js only supports string values as env parameters, while Vite supports several built-in envs as boolean (namely, SSR, DEV, PROD). To mimic Vite, set "truthy" values as env: '' instead of false, and '1' instead of true.

But beware that you cannot rely on import.meta.env.DEV === false in this case. Use !import.meta.env.DEV. This also affects simple assigning, not just vi.stubEnv method. :::

vi.unstubAllEnvs

Type: () => Vitest
Version: Since Vitest 0.26.0

Restores all import.meta.env and process.env values that were changed with vi.stubEnv. When it's called for the first time, Vitest remembers the original value and will store it, until unstubAllEnvs is called again.

import { vi } from 'vitest'

// `process.env.NODE_ENV` and `import.meta.env.NODE_ENV`
// are "development" before calling stubEnv

vi.stubEnv('NODE_ENV', 'production')

process.env.NODE_ENV === 'production'
import.meta.env.NODE_ENV === 'production'

vi.stubEnv('NODE_ENV', 'staging')

process.env.NODE_ENV === 'staging'
import.meta.env.NODE_ENV === 'staging'

vi.unstubAllEnvs()

// restores to the value that were stored before the first "stubEnv" call
process.env.NODE_ENV === 'development'
import.meta.env.NODE_ENV === 'development'

vi.stubGlobal

Type: (name: string | number | symbol, value: unknown) => Vitest

Changes the value of global variable. You can restore its original value by calling vi.unstubAllGlobals.

import { vi } from 'vitest'

// `innerWidth` is "0" before callling stubGlobal

vi.stubGlobal('innerWidth', 100)

innerWidth === 100
globalThis.innerWidth === 100
// if you are using jsdom or happy-dom
window.innerWidth === 100

:::tip You can also change the value by simply assigning it to globalThis or window (if you are using jsdom or happy-dom environment), but you won't be able to use vi.unstubAllGlobals to restore original value:

globalThis.innerWidth = 100
// if you are using jsdom or happy-dom
window.innerWidth = 100

:::

vi.unstubAllGlobals

Type: () => Vitest
Version: Since Vitest 0.26.0

Restores all global values on globalThis/global (and window/top/self/parent, if you are using jsdom or happy-dom environment) that were changed with vi.stubGlobal. When it's called for the first time, Vitest remembers the original value and will store it, until unstubAllGlobals is called again.

import { vi } from 'vitest'

const Mock = vi.fn()

// IntersectionObserver is "undefined" before calling "stubGlobal"

vi.stubGlobal('IntersectionObserver', Mock)

IntersectionObserver === Mock
global.IntersectionObserver === Mock
globalThis.IntersectionObserver === Mock
// if you are using jsdom or happy-dom
window.IntersectionObserver === Mock

vi.unstubAllGlobals()

globalThis.IntersectionObserver === undefined
'IntersectionObserver' in globalThis === false
// throws ReferenceError, because it's not defined
IntersectionObserver === undefined

vi.runAllTicks

Type: () => Vitest

Calls every microtask that was queued by proccess.nextTick. This will also run all microtasks scheduled by themselves.

vi.runAllTimers

Type: () => Vitest

This method will invoke every initiated timer until the timers queue is empty. It means that every timer called during runAllTimers will be fired. If you have an infinite interval, it will throw after 10 000 tries. For example this will log 1, 2, 3:
```
let i = 0
setTimeout(() => console.log(++i))
const interval = setInterval(() => {
  console.log(++i)
  if (i === 3)
    clearInterval(interval)

}, 50)

vi.runAllTimers()
```

vi.runAllTimersAsync

Type: () => Promise<Vitest>

This method will asynchronously invoke every initiated timer until the timers queue is empty. It means that every timer called during runAllTimersAsync will be fired even asynchronous timers. If you have an infinite interval, it will throw after 10 000 tries. For example this will log result:
```
setTimeout(async () => {
  console.log(await Promise.resolve('result'))
}, 100)

await vi.runAllTimersAsync()
```

vi.runOnlyPendingTimers

Type: () => Vitest

This method will call every timer that was initiated after vi.useFakeTimers() call. It will not fire any timer that was initiated during its call. For example this will only log 1:
```
let i = 0
setInterval(() => console.log(++i), 50)

vi.runOnlyPendingTimers()
```

vi.runOnlyPendingTimersAsync

Type: () => Promise<Vitest>

This method will asynchronously call every timer that was initiated after vi.useFakeTimers() call, even asynchronous ones. It will not fire any timer that was initiated during its call. For example this will log 2, 3, 3, 1:

setTimeout(() => {
  console.log(1)
}, 100)
setTimeout(() => {
  Promise.resolve().then(() => {
    console.log(2)
    setInterval(() => {
      console.log(3)
    }, 40)
  })
}, 10)

await vi.runOnlyPendingTimersAsync()

vi.setSystemTime

Type: (date: string | number | Date) => void

Sets current date to the one that was passed. All Date calls will return this date.

Useful if you need to test anything that depends on the current date - for example luxon calls inside your code.
```
const date = new Date(1998, 11, 19)

vi.useFakeTimers()
vi.setSystemTime(date)

expect(Date.now()).toBe(date.valueOf())

vi.useRealTimers()
```

vi.setConfig

Type: RuntimeConfig

Updates config for the current test file. You can only affect values that are used, when executing tests.

vi.spyOn

Type: <T, K extends keyof T>(object: T, method: K, accessType?: 'get' | 'set') => MockInstance

Creates a spy on a method or getter/setter of an object.

let apples = 0
const obj = {
  getApples: () => 13,
}

const spy = vi.spyOn(obj, 'getApples').mockImplementation(() => apples)
apples = 1

expect(obj.getApples()).toBe(1)

expect(spy).toHaveBeenCalled()
expect(spy).toHaveReturnedWith(1)

vi.stubGlobal

Type: (key: keyof globalThis & Window, value: any) => Vitest

Puts a value on global variable. If you are using jsdom or happy-dom, also puts the value on window object.

Read more in "Mocking Globals" section.

vi.unmock

Type: (path: string) => void

Removes module from the mocked registry. All calls to import will return the original module even if it was mocked before. This call is hoisted (moved) to the top of the file, so it will only unmock modules that were defined in setupFiles, for example.

vi.doUnmock

Type: (path: string) => void

The same as vi.unmock, but is not hoisted to the top of the file. The next import of the module will import the original module instead of the mock. This will not unmock previously imported modules.

// ./increment.js
export const increment = number => number + 1

import { increment } from './increment.js'

// increment is already mocked, because vi.mock is hoisted
increment(1) === 100

// this is hoisted, and factory is called before the import on line 1
vi.mock('./increment.js', () => ({ increment: () => 100 }))

// all calls are mocked, and `increment` always returns 100
increment(1) === 100
increment(30) === 100

// this is not hoisted, so other import will return unmocked module
vi.doUnmock('./increment.js')

// this STILL returns 100, because `vi.doUnmock` doesn't reevaluate a module
increment(1) === 100
increment(30) === 100

// the next import is unmocked, now `increment` is the original function that returns count + 1
const { increment: unmockedIncrement } = await import('./increment.js')

unmockedIncrement(1) === 2
unmockedIncrement(30) === 31

vi.useFakeTimers

Type: () => Vitest

To enable mocking timers, you need to call this method. It will wrap all further calls to timers (such as setTimeout, setInterval, clearTimeout, clearInterval, nextTick, setImmediate, clearImmediate, and Date), until vi.useRealTimers() is called.

The implementation is based internally on @sinonjs/fake-timers.

vi.useRealTimers

Type: () => Vitest

When timers are run out, you may call this method to return mocked timers to its original implementations. All timers that were run before will not be restored.

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Vi

vi.advanceTimersByTime

vi.advanceTimersByTimeAsync

vi.advanceTimersToNextTimer

vi.advanceTimersToNextTimerAsync

vi.getTimerCount

vi.clearAllMocks

vi.clearAllTimers

vi.dynamicImportSettled

vi.fn

vi.getMockedSystemTime

vi.getRealSystemTime

vi.mock

vi.doMock

vi.mocked

vi.importActual

vi.importMock

vi.resetAllMocks

vi.resetConfig

vi.resetModules

vi.restoreAllMocks

vi.restoreCurrentDate

vi.stubEnv

vi.unstubAllEnvs

vi.stubGlobal

vi.unstubAllGlobals

vi.runAllTicks

vi.runAllTimers

vi.runAllTimersAsync

vi.runOnlyPendingTimers

vi.runOnlyPendingTimersAsync

vi.setSystemTime

vi.setConfig

vi.spyOn

vi.stubGlobal

vi.unmock

vi.doUnmock

vi.useFakeTimers

vi.useRealTimers