I'm using `create-react-app` and writing my very first test in a React component, which isn't working. I haven't installed any additional packages in my application, so I'm only using what is bundled with create-react-app by default. Here is my **Button.js** component:

```
function Button(props) {

  if(props.classes) {
    for(let i = 0; i < props.classes.length; i++) {
       btnClasses += `${props.classes[i]} `;
    }
  }

  return (
    <button className={btnClasses}>
      {props.text}
    </button>
  );
}

```

The component itself works. I can set the `text` and `classes` props and use it like this:

`<Button text="My Button" classes={['myclass', 'myotherclass']} />`

I want to write a test that checks if the button has the class when I pass one as a prop. Here is my **Button.test.js**:

```
import React from 'react';
import { render, unmountComponentAtNode } from 'react-dom';
import { act } from 'react-dom/test-utils';

import Button from './Button';

let container = null;

beforeEach(() => {
  container = document.createElement('div');
  document.body.appendChild(container);
});

describe('Button', () => {

  it('renders with classes', () => {
    act(() => {
      render(<Button classes={['myclass']} />, container);
    });
    expect(container.classList.contains('myclass')).toBe(true);
  });
});

```

This test fails and I don't know why. I was under the impression that you can interact with `container` like any other DOM node. When I `console.log(container.classList)`, I get an empty `DOMTokenList {}`. What am I missing? Why doesn't this test work?