new_contents: # test_sf.py
  import unittest
  import io
  import sys
  import subprocess
  
  class TestSf(unittest.TestCase):
      """
      Test TestSf
      """
  
      def execute(self, command):
          proc = subprocess.Popen(
             command,
             stdout = subprocess.PIPE,
             stderr = subprocess.PIPE,
          )
          out,err = proc.communicate()
          return out, err, proc.returncode
  
      def test_help_arg_should_print_help_and_exit(self):
          out, err, code = self.execute([sys.executable, "sf.py", "-h"])
          self.assertIn(b"show this help message and exit", out)
          self.assertEqual(b"", err)
          self.assertEqual(0, code)
  
  if __name__ == '__main__':
      unittest.main()
  
  
subject: Add test/unit/test_sf.py stub