@jetshop/core/hooks/useChannelBanner.test.js

import { useChannelBanner } from './useChannelBanner';
import React from 'react';
import { act, render } from '@testing-library/react';
import { useCookies } from 'react-cookie';

jest.mock('react-cookie');

function mockedUseCookies() {
  return [{}, () => {}];
}

useCookies.mockImplementation(mockedUseCookies);

describe('useChannelBanner', () => {
  test('sets the banner to open by default', () => {
    const { hookValues } = setup();

    expect(hookValues.bannerIsOpen).toBe(true);
  });
  test('sets banner to closed if there is a hideBanner cookie', () => {
    useCookies.mockImplementation(() => {
      return [
        {
          hideBanner: 'true'
        },
        () => {}
      ];
    });

    const { hookValues } = setup();

    expect(hookValues.bannerIsOpen).toBe(false);
  });
  describe('hideTheBanner', () => {
    test('sets a cookie with the name of hideBanner and value true', () => {
      let cookieName;
      let value;

      useCookies.mockImplementation(() => {
        return [
          {},
          (a, b) => {
            [cookieName, value] = [a, b];
          }
        ];
      });

      const { hookValues } = setup();

      act(() => hookValues.hideTheBanner());

      expect(cookieName).toBe('hideBanner');
      expect(value).toBe(true);
    });
  });
});

function setup() {
  let hookValues;

  const utils = render(
    <Component>
      {returns => {
        hookValues = returns;
        return null;
      }}
    </Component>
  );

  return { ...utils, hookValues };
}

function Component({ children }) {
  const returns = useChannelBanner();

  return children(returns);
}