new_contents: from .cat import cat
  
  
  def test_cat(fs):
      filename = 'foo.txt'
      contents = 'insert a story here'
      fs.CreateFile(filename, contents=contents)
  
      result = cat(filename)
      assert result[0] == 'success'
      assert result[1] == contents
  
  
  def test_cat_missing(fs):
      result = cat('file.txt')
      assert result[0] == 'failure'
      assert result[1] is None
  
subject: add test for markdownify/cat