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Vitest · Method

vi.isMockFunction

vi.isMockFunction checks whether a value is a Vitest mock function. In TypeScript, a successful check narrows the value to Mock.

Last updated 2 November 2026

Syntax

function isMockFunction ( fn: unknown ): asserts fn is Mock

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vi.fn
vi.spyOn
vi.clearAllMocks
vi.resetAllMocks

Source: Vi | Vitest. Checked 2026-11-03.