How to properly make mock throw an error in Jest?

How to properly make mock throw an error in Jest?


I’m testing my GraphQL api using Jest.

I’m using a separate test suit for each query/mutation

I have 2 tests (each one in a separate test suit) where I mock one function (namely, Meteor’s callMethod) that is used in mutations.

  it('should throw error if email not found', async () => {
      .mockReturnValue(new Error('User not found [403]'))

    const params = { email: '[email protected]' };

    const result = await simulateQuery({ query, params });


    // test logic
    expect(callMethod).toBeCalledWith({}, 'forgotPassword', {
      email: '[email protected]',

    // test resolvers

When I console.log(result) I get

{ data: { forgotPassword: true } }

This behaviour is not what I want because in .mockReturnValue I throw an Error and therefore expect result to have an error object

Before this test, however, another is ran

 it('should throw an error if wrong credentials were provided', async () => {
      .mockReturnValue(new Error('cannot login'))

And it works fine, the error is thrown

I guess the problem is that mock doesn’t get reset after the test finishes.
In my jest.conf.js I have clearMocks: true

Each test suit is in a separate file, and I mock functions before tests like this:

import simulateQuery from '../../../helpers/simulate-query';

import callMethod from '../../../../imports/api/users/functions/auth/helpers/call-accounts-method';

import LOGIN_WITH_PASSWORD_MUTATION from './mutations/login-with-password';


describe('loginWithPassword mutation', function() {


When I substituted .mockReturnValue with .mockImplementation everything worked out as expected:

callMethod.mockImplementation(() => {
  throw new Error('User not found');

But that doesn’t explain why in another test .mockReturnValue works fine…

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  • 1

    It looks like your mock is returning an error object, not throwing it. Without seeing your code that you are testing, I can only share the experience I had. I forgot to mock a function called in my mutation, which caused an error to be thrown unintentionally. Perhaps there is something similar happening for you?

    – Rhuarc13

    May 14, 2018 at 13:54

3 Answers

Reset to default


Change .mockReturnValue with .mockImplementation:

    yourMockInstance.mockImplementation(() => {
      throw new Error();

in case you want to assert

   test('the fetch fails with an error', () => {
     return expect(fetchData()).rejects.toMatch('error');

If it’s a promise you can also to .rejects–rejects

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  • 1

    cool. How to handle it and make and assert?

    – Dmytro

    Feb 19, 2021 at 23:00

  • 2

    it throws the error but then the test fails because it has thrown an error. how do we assert?

    – schlingel

    Mar 7, 2022 at 7:36


For promises, can use

test('async test', async () => {
  const asyncMock = jest.fn().mockRejectedValue(new Error('Async error'));

  await asyncMock(); // throws "Async error"

For testing that error was thrown or not, can use

const func = () => {
  throw new Error('my error')
it('should throw an error', () => {

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  • 1

    You would also need a try and catch in your expect otherwise it would not assert correctly. Can you please improve your answer or reply if I am missing something.

    – MG Developer

    Nov 24, 2021 at 16:57

  • 1

    @MGDeveloper we dont need try-catch while unit testing and using toThrow() ( If you try that in your tests, it should work. Can also test in here :… (sandbox content is transient though). I did edit the terminology from “handling” to “testing” if that was confusing

    – gawkface

    Nov 27, 2021 at 3:42

  • 1

    I found the mockRejectedValue helpful in the case that the asynchronous unit I was testing handled the exception thrown in a specific way that I wanted to test, therefore in that case a catch or toThrow() would not be needed.

    – CortexCompiler

    Aug 10, 2022 at 19:31


For Angular + Jest:

import { throwError } from 'rxjs';

yourMockInstance.mockImplementation(() => {
  return throwError(new Error('my error message'));

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  • 2

    Technically this isn’t a throw in the pure JS sense. You are configuring the mock to return a RXJS observable object which immediately emits an error notification. Still, maybe handy for folks to see here. The accepted answer certainly will make a mock throw an error. In all cases.

    – Zach Lysobey

    Sep 16, 2020 at 21:57

  • Only returning throw Error should be enough: yourMockInstance.mockImplementation(() => throwError('my error message'));

    – manzapanza

    Apr 30, 2021 at 21:42

  • Actually using mockReturnValue is enough: mockInstance.mockReturnValue(throwError(() => new Error('my error message')))

    – RcoderNY

    Jun 19, 2022 at 5:41

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