1 files changed, 11 insertions, 0 deletions
diff --git a/Lib/test/test_dbm_gnu.py b/Lib/test/test_dbm_gnu.py
index 16b7fe6fac..f1c7d34085 100644
--- a/Lib/test/test_dbm_gnu.py
+++ b/Lib/test/test_dbm_gnu.py
@@ -131,6 +131,17 @@ class TestGdbm(unittest.TestCase):
             self.assertEqual(db['Unicode key \U0001f40d'],
                              'Unicode value \U0001f40d'.encode())
 
+    def test_write_readonly_file(self):
+        with gdbm.open(filename, 'c') as db:
+            db[b'bytes key'] = b'bytes value'
+        with gdbm.open(filename, 'r') as db:
+            with self.assertRaises(gdbm.error):
+                del db[b'not exist key']
+            with self.assertRaises(gdbm.error):
+                del db[b'bytes key']
+            with self.assertRaises(gdbm.error):
+                db[b'not exist key'] = b'not exist value'
+
     @unittest.skipUnless(TESTFN_NONASCII,
                          'requires OS support of non-ASCII encodings')
     def test_nonascii_filename(self):