How to test methods inside functional component using enzyme as instance() returns null for shallow wrapper?

From this docs: https://airbnb.io/enzyme/docs/api/ShallowWrapper/instance.html

NOTE: can only be called on a wrapper instance that is also the root instance. With React 16 and above, instance() returns null for stateless functional components.

Test component behavior, not implementation details.

E.g.

index.jsx:

import React, { useState } from 'react';const Counter = () => {  const [counter, setCounter] = useState(0);  const incCounter = () => {    setCounter(counter + 1);  };  return (    <>      <p>Counter value is: {counter}</p>      <button className="increment" onClick={incCounter}>        Up      </button>    </>  );};export default Counter;

index.spec.jsx:

import React from 'react';import Counter from './';import { shallow } from 'enzyme';describe('Counter', () => {  let counter;  beforeEach(() => {    counter = shallow(<Counter />);  });  it('calls incCounter function when button is clicked', () => {    expect(counter.find('p').text()).toBe('Counter value is: 0');    const incButton = counter.find('button');    incButton.simulate('click');    expect(counter.find('p').text()).toBe('Counter value is: 1');  });});

Unit test result with 100% coverage:

 PASS  src/stackoverflow/59475724/index.spec.jsx (10.045s)  Counter    ✓ calls incCounter function when button is clicked (17ms)-----------|----------|----------|----------|----------|-------------------|File       |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |-----------|----------|----------|----------|----------|-------------------|All files  |      100 |      100 |      100 |      100 |                   | index.jsx |      100 |      100 |      100 |      100 |                   |-----------|----------|----------|----------|----------|-------------------|Test Suites: 1 passed, 1 totalTests:       1 passed, 1 totalSnapshots:   0 totalTime:        11.697s

Source code: https://github.com/mrdulin/jest-codelab/tree/master/src/stackoverflow/59475724