old_contents: import os.path
  from test.support import run_unittest
  import unittest
  
  
  def test_main():
      start_dir = os.path.dirname(__file__)
      top_dir = os.path.dirname(os.path.dirname(start_dir))
      test_loader = unittest.TestLoader()
      run_unittest(test_loader.discover(start_dir, top_level_dir=top_dir))
  
  
  if __name__ == '__main__':
      test_main()
  
new_contents: import importlib
  from importlib.test.import_ import util
  import os.path
  from test.support import run_unittest
  import sys
  import unittest
  
  
  def test_main():
      start_dir = os.path.dirname(__file__)
      top_dir = os.path.dirname(os.path.dirname(start_dir))
      test_loader = unittest.TestLoader()
      if '--builtin' in sys.argv:
          util.using___import__ = True
      run_unittest(test_loader.discover(start_dir, top_level_dir=top_dir))
  
  
  if __name__ == '__main__':
      test_main()
  
subject: Add support for a --builtin argument to importlib.test to trigger running import-specific tests with __import__ instead of importlib.