def METHOD_NAME():
    """
    Check that when device changes to index out of range,
    the device selector emits None on the device_changed signal
    """
    device_selector = mu.interface.main.DeviceSelector()
    device_selector.device_changed = mock.MagicMock()
    device_selector._device_changed(-1)
    device_selector.device_changed.emit.assert_called_once_with(None)