text: try:
      from . import generic as g
  except BaseException:
      import generic as g
  
  
  class ValidTest(g.unittest.TestCase):
  
      def test_validate(self):
  
          for validate in [True, False]:
              m = g.get_mesh('featuretype.STL', validate=validate)
  
              # reverse all face windings and normals to make volume negative
              m.invert()
  
              m._cache.verify()
              assert 'face_normals' in m._cache
              if validate:
                  assert m.volume > 0.0
              else:
                  assert m.volume < 0.0
              m._cache.verify()
              assert 'face_normals' in m._cache
  
  
  if __name__ == '__main__':
      g.trimesh.util.attach_to_log()
      g.unittest.main()
  