old_contents: import glob
  import itertools as it
  import os
  
  import parmed as pmd
  from pkg_resources import resource_filename
  import pytest
  
  from foyer import Forcefield
  from foyer.tests.utils import atomtype
  from foyer.xml_writer import write_foyer
  
  def test_write_xml(filename, ff_file):
     structure = pmd.loadfile(filename)
     forcefield = Forcefield(ff_file)
  
     structure.write_foyer('test.xml', forcefield=forcefield)
  
  def test_load_xml():
     structure = pmd.loadfile(filename)
     forcefield = Forcefield(ff_file)
  
     structure.write_foyer('test.xml', forcefield=forcefield)
  
     generated_ff = Forcefield('text.xml')
  
new_contents: import parmed as pmd
  import pytest
  import os
  
  from pkg_resources import resource_filename
  from foyer import Forcefield
  from foyer.xml_writer import write_foyer
  
  
  OPLS_TESTFILES_DIR = resource_filename('foyer', 'opls_validation')
  
  def test_write_xml():
      top = os.path.join(OPLS_TESTFILES_DIR, 'benzene/benzene.top')
      gro = os.path.join(OPLS_TESTFILES_DIR, 'benzene/benzene.gro')
      structure = pmd.load_file(top, xyz=gro)
      forcefield = Forcefield(name='oplsaa')
      param_struc = forcefield.apply(structure)
  
      param_struc.write_foyer('test.xml', forcefield=forcefield)
  
  def test_load_xml():
      top = os.path.join(OPLS_TESTFILES_DIR, 'benzene/benzene.top')
      gro = os.path.join(OPLS_TESTFILES_DIR, 'benzene/benzene.gro')
      structure = pmd.load_file(top, xyz=gro)
      forcefield = Forcefield(name='oplsaa')
      param_struc = forcefield.apply(structure)
  
      param_struc.write_foyer('test.xml', forcefield=forcefield)
  
      generated_ff = Forcefield('test.xml')
  
subject: Update xml writer test to work