require-mock-type-parameters.md

Enforce using type parameters with vitest mock functions (vitest/require-mock-type-parameters)

⚠️ This rule warns in the 🌐 all config.

When using vi.fn() to mock functions, by default, the mocked function has the type of (...args: any[]) => any. To add more specific types to the mocked function, a type parameter needs to be added to the call, e.g. vi.fn<(arg1: string, arg2: boolean) => number>().

Additionally, there are two more mock functions with type parameters that cannot be automatically inferred by the TypeScript compiler, vi.importActual and vi.importMock. This rule doesn't by default report these function, however, the check can be enabled by setting the checkImportFunctions rule option.

The following patterns are considered bad:

import { vi } from 'vitest'

test('foo', () => {
  const myMockedFn = vi.fn()
})

The following patterns are considered OK:

import { vi } from 'vitest'

test('foo', () => {
  const myMockedFnOne = vi.fn<(arg1: string, arg2: boolean) => number>()
  const myMockedFnTwo = vi.fn<() => void>()
  const myMockedFnThree = vi.fn<any>()
})

Options

{
  "vitest/require-hook": ["error", {
	"checkImportFunctions": false
  }]
}

The following patterns are considered bad with checkImportFunctions: true:

import { vi } from 'vitest'

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

  return { ...originalModule }
})

const fs = await vi.importMock('fs')