How to check DOM element with jest?

Question

JavaScript

there is a function that adds or removes a class from an element:

export default function activeButtonClick(button) {
  if (button.classList.contains('active')) {
    button.classList.remove('active');
  } else {
    button.classList.add('active');
  }
}
module.exports = activeButtonClick;

What is the correct way to write a test that checks that the input DOM element now has the 'active' class?
my sketch:

const activeBtn = require('./activeBtnClick');
const pencil = document.getElementById('pencil');

describe("activeBtnClick", () => {
  it("adds class to the button", () => {
    ??
  });

});

Answer 1

const activeBtn = require('./activeBtnClick');
const pencil = document.getElementById('pencil');

describe("activeBtnClick", () => {
  it("adds class to the button", () => {
     except(button.classList.contains('active')).toEqual(true);
  });
});