JavaScript programatically check if camera is being used

I'm writing functional tests for a video chat app.

I want to make sure that when the user leaves the meeting the camera turns off. So, I'm trying to check if the camera is being used or not.

Is there a way to do that programatically? I couldn't find any methods on navigator.MediaDevices that say "hey your camera is being used".

Here is how I solved it in TestCafe by "spying" on getUserMedia:

const overWriteGetUserMedia = ClientFunction(() => {
  const realGetUserMedia = navigator.mediaDevices.getUserMedia;
  const allRequestedTracks = [];
  navigator.mediaDevices.getUserMedia = constraints =>
    realGetUserMedia(constraints).then(stream => {
      stream.getTracks().forEach(track => {
        allRequestedTracks.push(track);
      });
      return stream;
    });
  return allRequestedTracks;
});

test('leaving a meeting should end streams', async t => {
  const allRequestedTracks = await overWriteGetUserMedia();

  await t.wait(5000); // wait for streams to start;

  await t.click(screen.getByLabelText(/leave/i));
  await t.click(screen.getByLabelText(/yes, leave the meeting/i));

  await t.wait(1000); // wait for navigation;

  const actual = !allRequestedTracks.some(track => !track.ended);
  const expected = true;

  await t.expect(actual).eql(expected);
});