def METHOD_NAME(membrane_xtc, univ):
    # regression test the data structures
    # generated by the 2D streamplot code
    u1, v1, avg, std = streamlines.generate_streamlines(topology_file_path=Martini_membrane_gro,
                                                        trajectory_file_path=membrane_xtc,
                                                        grid_spacing=20,
                                                        MDA_selection='name PO4',
                                                        start_frame=1,
                                                        end_frame=2,
                                                        xmin=univ.atoms.positions[...,0].min(),
                                                        xmax=univ.atoms.positions[...,0].max(),
                                                        ymin=univ.atoms.positions[...,1].min(),
                                                        ymax=univ.atoms.positions[...,1].max(),
                                                        maximum_delta_magnitude=2.0,
                                                        num_cores=1)
    assert_allclose(u1, np.array([[0.79999924, 0.79999924, 0.80000687, 0.79999542, 0.79998779],
                                  [0.80000019, 0.79999542, 0.79999924, 0.79999542, 0.80001068],
                                  [0.8000021, 0.79999924, 0.80001068, 0.80000305, 0.79999542],
                                  [0.80000019, 0.79999542, 0.80001068, 0.80000305, 0.80000305],
                                  [0.79999828, 0.80000305, 0.80000305, 0.80000305, 0.79999542]]))
    assert_allclose(v1, np.array([[0.53999901, 0.53999996, 0.53999996, 0.53999996, 0.54000092],
                                  [0.5399971, 0.54000092, 0.54000092, 0.54000092, 0.5399971 ],
                                  [0.54000473, 0.54000473, 0.54000092, 0.5399971, 0.54000473],
                                  [0.54000092, 0.53999329, 0.53999329, 0.53999329, 0.54000092],
                                  [0.54000092, 0.53999329, 0.53999329, 0.54000092, 0.53999329]]))
    assert avg == pytest.approx(0.965194167)
    assert std == pytest.approx(4.444808820e-06)