def METHOD_NAME(statepoint_filename):
    with openmc.StatePoint(statepoint_filename) as sp:
        flux_tally = sp.tallies[1]
        mesh = flux_tally.find_filter(openmc.MeshFilter).mesh
        neutron_flux = flux_tally.get_reshaped_data().squeeze()
        # we expect the tally results to be the same as the mesh grid width
        # for these cases
        d_r = mesh.r_grid[1] - mesh.r_grid[0]
        assert neutron_flux == pytest.approx(d_r)