chai-enzyme delayed loading example

spec_helper_jest.js

import chai from 'chai';
// This is not really a mock, but jest prevents out of scope
// variables unless prefixed with "mock".
const mockChai = chai;
let mockSetup = false;
// Here we're "mocking" enzyme, so that we can delay loading of
// the utility functions until emzyme is imported in tests.
jest.mock('enzyme', () => {
  const actualEnzyme = require.requireActual('enzyme');
  if (!mockSetup) {
    const chaiEnzyme = require.requireActual('chai-enzyme');
    if (typeof chaiEnzyme === 'function' && !mockSetup) {
      mockSetup = true;
      mockChai.use(chaiEnzyme());
    }
  }
  return actualEnzyme;
});