CODE EXAMPLE FOR JAVASCRIPT

mock a function jest react

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

import { randomNameGenerator } from "./utils";

jest.mock('./utils.js', () => ({ 
  randomNameGenerator: jest.fn()
}));

describe('test', () => {
  it('allows Jest method mocking 1', () => {
    randomNameGenerator.mockImplementation(() => "Craig");
    const { getByText } = render(<App />);
    expect(getByText("Craig")).toBeInTheDocument()
  });

  it('allows Jest method mocking 2', () => {
    randomNameGenerator.mockImplementation(() => "Not Craig");
    const { getByText } = render(<App />);
    expect(getByText("Not Craig")).toBeInTheDocument()
  });
});