old_contents: from xenon import (FileSystem)
  
  
  def test_path_separator(xenon_server, tmpdir):
      with FileSystem.create(adaptor='file') as filesystem:
          assert filesystem.get_path_separator() == '/'
  
new_contents: import pytest
  from xenon import (FileSystem, Path, PathAlreadyExistsException)
  
  
  def test_path_separator(xenon_server, tmpdir):
      with FileSystem.create(adaptor='file') as filesystem:
          assert filesystem.get_path_separator() == '/'
  
  
  def test_path_already_exists_error(xenon_server, tmpdir):
      with FileSystem.create(adaptor='file') as filesystem:
          with pytest.raises(PathAlreadyExistsException):
              filesystem.create_directory(Path('test'))
              filesystem.create_directory(Path('test'))
  
subject: add unittest for PathAlreadyExistsException