Checking `picker-container` doesn’t make much sense because that’s the selector you use to get the element. Besides, selecting `.picker-container` is not very robust because there are several elements matching this (time and date pickers).

Something like this (untested) should be used instead:
```javascript
  var container = document.querySelector('#time-picker .picker-container');
  assert.ok(container.classList.contains('format12h'));
```