old_contents: import os
  import tempfile
  import subprocess
  import sys
  from os.path import dirname, abspath, isfile, join
  
  from pywincffi.dev.release import check_wheel
  from pywincffi.dev.testutil import TestCase
  
  
  class TestWheel(TestCase):
      """
      Tests for constants of :func:`pywincffi.dev.release.test_wheel`
      """
      def test_fails(self):
          fd, path = tempfile.mkstemp()
          self.addCleanup(os.remove, path)
  
          with os.fdopen(fd, "w") as file_:
              file_.write("")
  
          self.assertFalse(check_wheel(path))
  
      def test_success(self):
          root_dir = dirname(dirname(dirname(abspath(__file__))))
  
          # Be sure this exists otherwise the command below may fail for
          # unexpected reasons.
          setup_py = join(root_dir, "setup.py")
          self.assertTrue(isfile(setup_py), "%s does not exist" % setup_py)
  
          # Build pywincffi.  We should always be able to unpack our own
          # library and this also gives us a way to test wheel build directly.
          process = subprocess.Popen(
              [sys.executable, "setup.py", "bdist_wheel"],
              stderr=subprocess.PIPE, stdout=subprocess.PIPE, cwd=root_dir)
          process.communicate()
          self.assertEqual(process.returncode, 0)
  
          for root, _, files in os.walk(join(root_dir, "dist")):
              for filename in files:
                  path = join(root, filename)
                  self.assertTrue(check_wheel(path), path)
  
new_contents: import os
  import tempfile
  import subprocess
  import sys
  from os.path import dirname, abspath, isfile, join
  
  from pywincffi.dev.release import check_wheel
  from pywincffi.dev.testutil import TestCase
  
  
  class TestWheel(TestCase):
      """
      Tests for constants of :func:`pywincffi.dev.release.test_wheel`
      """
      def test_fails(self):
          fd, path = tempfile.mkstemp()
          self.addCleanup(os.remove, path)
  
          with os.fdopen(fd, "w") as file_:
              file_.write("")
  
          self.assertFalse(check_wheel(path))
  
      def test_success(self):
          root_dir = dirname(dirname(dirname(abspath(__file__))))
  
          # Be sure this exists otherwise the command below may fail for
          # unexpected reasons.
          setup_py = join(root_dir, "setup.py")
          self.assertTrue(isfile(setup_py), "%s does not exist" % setup_py)
  
          # Build pywincffi.  We should always be able to unpack our own
          # library and this also gives us a way to test wheel build directly.
          process = subprocess.Popen(
              [sys.executable, "setup.py", "bdist_wheel"],
              stderr=subprocess.PIPE, stdout=subprocess.PIPE, cwd=root_dir)
          process.communicate()
          self.assertEqual(process.returncode, 0)
  
          for root, _, files in os.walk(join(root_dir, "dist")):
              for filename in files:
                  if filename.endswith(".whl"):
                      path = join(root, filename)
                      self.assertTrue(check_wheel(path), path)
  
subject: check the file extension we're passing in