From 16c6759b3748f9b787b2fa4d5e652a8e08a17dee Mon Sep 17 00:00:00 2001
From: Serhiy Storchaka <storchaka@gmail.com>
Date: Sat, 3 Sep 2022 08:58:25 +0300
Subject: [PATCH] gh-45108: Improve docstring and testing of ZipFile.testfile()
 (GH-96233)

---
 Lib/test/test_zipfile.py   |  9 +++++----
 Lib/test/test_zipfile64.py | 11 ++++-------
 Lib/zipfile.py             |  5 ++++-
 3 files changed, 13 insertions(+), 12 deletions(-)

diff --git a/Lib/test/test_zipfile.py b/Lib/test/test_zipfile.py
index 21257785159..6f6f4bc26b0 100644
--- a/Lib/test/test_zipfile.py
+++ b/Lib/test/test_zipfile.py
@@ -124,8 +124,9 @@ def zip_test(self, f, compression, compresslevel=None):
                 self.assertEqual(info.filename, nm)
                 self.assertEqual(info.file_size, len(self.data))
 
-            # Check that testzip doesn't raise an exception
-            zipfp.testzip()
+            # Check that testzip thinks the archive is ok
+            # (it returns None if all contents could be read properly)
+            self.assertIsNone(zipfp.testzip())
 
     def test_basic(self):
         for f in get_files(self):
@@ -748,8 +749,8 @@ def zip_test(self, f, compression):
                 self.assertEqual(info.filename, nm)
                 self.assertEqual(info.file_size, len(self.data))
 
-            # Check that testzip doesn't raise an exception
-            zipfp.testzip()
+            # Check that testzip thinks the archive is valid
+            self.assertIsNone(zipfp.testzip())
 
     def test_basic(self):
         for f in get_files(self):
diff --git a/Lib/test/test_zipfile64.py b/Lib/test/test_zipfile64.py
index 0947013afbc..be654a8478b 100644
--- a/Lib/test/test_zipfile64.py
+++ b/Lib/test/test_zipfile64.py
@@ -32,10 +32,6 @@ def setUp(self):
         line_gen = ("Test of zipfile line %d." % i for i in range(1000000))
         self.data = '\n'.join(line_gen).encode('ascii')
 
-        # And write it to a file.
-        with open(TESTFN, "wb") as fp:
-            fp.write(self.data)
-
     def zipTest(self, f, compression):
         # Create the ZIP archive.
         with zipfile.ZipFile(f, "w", compression) as zipfp:
@@ -67,6 +63,9 @@ def zipTest(self, f, compression):
                     (num, filecount)), file=sys.__stdout__)
                     sys.__stdout__.flush()
 
+            # Check that testzip thinks the archive is valid
+            self.assertIsNone(zipfp.testzip())
+
     def testStored(self):
         # Try the temp file first.  If we do TESTFN2 first, then it hogs
         # gigabytes of disk space for the duration of the test.
@@ -85,9 +84,7 @@ def testDeflated(self):
         self.zipTest(TESTFN2, zipfile.ZIP_DEFLATED)
 
     def tearDown(self):
-        for fname in TESTFN, TESTFN2:
-            if os.path.exists(fname):
-                os.remove(fname)
+        os_helper.unlink(TESTFN2)
 
 
 class OtherTests(unittest.TestCase):
diff --git a/Lib/zipfile.py b/Lib/zipfile.py
index 903d09dc023..b6465373c10 100644
--- a/Lib/zipfile.py
+++ b/Lib/zipfile.py
@@ -1468,7 +1468,10 @@ def printdir(self, file=None):
                   file=file)
 
     def testzip(self):
-        """Read all the files and check the CRC."""
+        """Read all the files and check the CRC.
+
+        Return None if all files could be read successfully, or the name
+        of the offending file otherwise."""
         chunk_size = 2 ** 20
         for zinfo in self.filelist:
             try: