jest mock useeffect return code example

Example 1: How to test useEffect in react testing library

import { List } from './';
import React from 'react';
import '@testing-library/jest-dom/extend-expect';
import { render, waitForElement } from '@testing-library/react';

describe('59892259', () => {
  let originFetch;
  beforeEach(() => {
    originFetch = (global as any).fetch;
  });
  afterEach(() => {
    (global as any).fetch = originFetch;
  });
  it('should pass', async () => {
    const fakeResponse = { title: 'example text' };
    const mRes = { json: jest.fn().mockResolvedValueOnce(fakeResponse) };
    const mockedFetch = jest.fn().mockResolvedValueOnce(mRes as any);
    (global as any).fetch = mockedFetch;
    const { getByTestId } = render(<List></List>);
    const div = await waitForElement(() => getByTestId('test'));
    expect(div).toHaveTextContent('example text');
    expect(mockedFetch).toBeCalledTimes(1);
    expect(mRes.json).toBeCalledTimes(1);
  });
});

Example 2: how to test useeffect with enzyme

import React from "react";
import { render, unmountComponentAtNode } from "react-dom";
import { act } from "react-dom/test-utils";

import Contact from "./contact";
import MockedMap from "./map";

jest.mock("./map", () => {
  return function DummyMap(props) {
    return (
      <p>A dummy map.</p>
    );
  };
});

it("should render contact information", () => {
  const center = { lat: 0, long: 0 };
  act(() => {
    render(
      <Contact
        name="Joni Baez"
        email="[email protected]"
        site="http://test.com"
        center={center}
      />,
      container
    );
  });
});