Does Jest reset the JSDOM document after every suite or test?

To correct the (misleading) accepted answer and explicitly underline that very important bit of information from one of the previous comments:

No. Jest does not clean the JSDOM document after each test run! It only clears the DOM after all tests inside an entire file are completed.

That means that you have to manually cleanup your resources created during a test, after every single test run. Otherwise it will cause shared state, which results in very subtle errors that can be incredibly hard to track.

The following is a very simple, yet effective method to cleanup the JSDOM after each single test inside a jest test suite:

describe('my test suite', () => {
  afterEach(() => {
    document.getElementsByTagName('html')[0].innerHTML = ''; 
  });

  // your tests here ...
});