createMockFn

function in meocord/testing Since 4.0.0

createMockFn<
  T extends (...args: any[]) => any = (...args: any[]) => any,
>(impl?: T): MockedFunction<T>

Creates a mock function that jest's and Vitest's expect both read.

Use it for a function double in code that must not depend on one test runner, such as a shared test helper; in a Vitest test, vi.fn() works as well. clearAllMocks and resetAllMocks reach it. Once useMockFn registers a runner's function, it returns that runner's mock.

Parameters

Name	Type	Description
`impl?`	`T`	The implementation to run until another is set.

Returns

MockedFunction<T>

Examples

TypeScript

import { expect } from 'vitest'

const double = createMockFn((value: number) => value * 2)
expect(double(2)).toBe(4)
double.mockReturnValueOnce(99)
expect(double(2)).toBe(99)
expect(double).toHaveBeenCalledTimes(2)