def METHOD_NAME(get_fn):
    # one of these files has PBCs and the other doesnt
    for fn in ['2EQQ.pdb', '4ZUO.pdb']:
        t = md.load(get_fn(fn))
        result = md.wernet_nilsson(t)
        assert len(result) == len(t)
        assert isinstance(result, list)
        assert all(isinstance(elem, np.ndarray) for elem in result)
        assert all(elem.shape[1] == 3 for elem in result)
        for frame, hbonds in enumerate(result):
            for d_i, h_i, a_i in hbonds:
                assert t.topology.atom(d_i).element.symbol in ['O', 'N']
                assert t.topology.atom(h_i).element.symbol == 'H'
                assert t.topology.atom(a_i).element.symbol in ['O', 'N']
            # assert that the donor-acceptor distance is less than 0.5 nm, just
            # to make sure the criterion is giving back totally implausible stuff
            if len(hbonds) > 0:
                assert np.all(md.compute_distances(t[frame], hbonds[:, [0, 2]]) < 0.5)