Mock 3rd party class with Jest in Typescript

jest-mocked-class.test.ts

import routeHandler from '../src/routeHandler';
import { mockResponse, mockRequest } from './test-helpers';

jest.mock('@googlemaps/google-maps-services-js');
import { Client } from '@googlemaps/google-maps-services-js';

const mockClient = {
  geocode: jest.fn(),
};

(Client as jest.Mock).mockImplementation(() => mockClient);

describe('routeHandler', () => {
  it('should call Google geocoder and return', async () => {
    const req = mockRequest();
    const res = mockResponse();

    mockClient.geocode.mockResolvedValue('kissa');

    await routeHandler(req, res, jest.fn());

    expect(res.send).toHaveBeenCalledWith({ result: 'kissa' });
  });
});

test-helpers.ts

import type { Response, Request } from 'express';

export const mockResponse = (opts?: Partial<Response>): Response =>
  (({
    send: jest.fn(),
    json: jest.fn(),
    status: jest.fn(),
    ...opts,
  } as unknown) as Response);

export const mockRequest = (opts?: Partial<Request>): Request =>
  (({
    body: {},
    ...opts,
  } as unknown) as Request);

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