commit ff9147d93b868f0e13b9fe14e2a76c2879f6787b
author Jan Mazur <16736821+mzr@users.noreply.github.com> Mon Sep 28 20:53:33 2020 +0200
committer GitHub <noreply@github.com> Mon Sep 28 21:53:33 2020 +0300
tree fbfb36ce08a859c0ce11a8247b311083933f8d3c
parent a195bceff7b552c5f86dec7894ff24dcc87235da

bpo-40105: ZipFile truncate in append mode with shorter comment (GH-19337)

Lib/test/test_zipfile.py

diff --git a/Lib/test/test_zipfile.py b/Lib/test/test_zipfile.py
index 2851051..687e43d 100644
--- a/Lib/test/test_zipfile.py
+++ b/Lib/test/test_zipfile.py
@@ -1856,11 +1856,14 @@
             self.assertEqual(zipf.comment, b"an updated comment")
 
         # check that comments are correctly shortened in append mode
+        # and the file is indeed truncated
         with zipfile.ZipFile(TESTFN,mode="w") as zipf:
             zipf.comment = b"original comment that's longer"
             zipf.writestr("foo.txt", "O, for a Muse of Fire!")
+        original_zip_size = os.path.getsize(TESTFN)
         with zipfile.ZipFile(TESTFN,mode="a") as zipf:
             zipf.comment = b"shorter comment"
+        self.assertTrue(original_zip_size > os.path.getsize(TESTFN))
         with zipfile.ZipFile(TESTFN,mode="r") as zipf:
             self.assertEqual(zipf.comment, b"shorter comment")