vitest-dev/vitest · error · TypeError

[vitest] Redirect mocks require a redirect string.

Error message

[vitest] Redirect mocks require a redirect string.

What it means

Redirect mocks point one module specifier at another real module; the 5th argument must be the redirect target specifier string. A non-string (or omitted) value means the registry cannot resolve where to redirect imports.

Source

Thrown at packages/mocker/src/registry.ts:123

    if (type === 'manual') {
      if (typeof factoryOrRedirect !== 'function') {
        throw new TypeError('[vitest] Manual mocks require a factory function.')
      }
      const mock = new ManualMockedModule(raw, id, url, factoryOrRedirect)
      this.add(mock)
      return mock
    }
    else if (type === 'automock' || type === 'autospy') {
      const mock = type === 'automock'
        ? new AutomockedModule(raw, id, url)
        : new AutospiedModule(raw, id, url)
      this.add(mock)
      return mock
    }
    else if (type === 'redirect') {
      if (typeof factoryOrRedirect !== 'string') {
        throw new TypeError('[vitest] Redirect mocks require a redirect string.')
      }
      const mock = new RedirectedModule(raw, id, url, factoryOrRedirect)
      this.add(mock)
      return mock
    }
    else {
      throw new Error(`[vitest] Unknown mock type: ${type}`)
    }
  }

  public delete(id: string): void {
    this.registryByUrl.delete(id)
  }

  public deleteById(id: string): void {
    this.registryById.delete(id)
  }

View on GitHub (pinned to d568f8ce37)

Solutions

1. Pass the redirect target as a string: `registry.register('redirect', raw, id, url, './real-module')`.
2. Remember the 5th arg is a function for `'manual'` but a string for `'redirect'`.
3. Resolve the target specifier before registering.

Example fix

// before
registry.register('redirect', raw, id, url)

// after
registry.register('redirect', raw, id, url, './__mocks__/fs')

function registerRedirect(registry: any, raw: string, id: string, url: string, target: unknown) {
  if (typeof target !== 'string' || target.length === 0) {
    throw new TypeError(`Redirect mocks require a non-empty target string, got ${typeof target}`)
  }
  registry.register('redirect', raw, id, url, target)
}

When it happens

Trigger: Calling `registry.register('redirect', raw, id, url)` (target omitted) or passing a non-string such as a function or number.

Common situations: Confusing the manual (factory) and redirect (string target) overloads; forgetting the target specifier; refactor dropping the argument.

Related errors

• Unknown mock type: ${(event as any).type}
• [vitest] Mocks require a raw string.
• [vitest] Mocks require a url string.
• [vitest] Mocks require an id string.
• [vitest] Manual mocks require a factory function.

AI-assisted analysis of vitest-dev/vitest@d568f8ce37 (2026-08-03). Data as JSON: /data/errors/2bd62ecf300cc23f.json. Report an issue: GitHub.