def METHOD_NAME(process_group_backend, device_str, expected_process_group_backend):
    """Test settings for process group backend."""
    class MockDDPStrategy(DDPStrategy):
        def __init__(self, root_device, process_group_backend):
            self._root_device = root_device
            super().__init__(process_group_backend=process_group_backend)
        @property
        def root_device(self):
            return self._root_device
    strategy = MockDDPStrategy(process_group_backend=process_group_backend, root_device=torch.device(device_str))
    assert strategy._get_process_group_backend() == expected_process_group_backend