def test_fires_callbacks_data_received():
progress = ProgressListener(upload_id='foo')
cb = mock.Mock()
progress.register_callback(cb)
progress.data_received(42)
assert len(cb.mock_calls) == 1
_, call_args, call_kwargs = cb.mock_calls[0]
state = call_args[0]
assert not state['files']
assert state['total'] == [42, None]
