#15222: Insert blank line after each message in mbox mailboxes

Lib/test/test_mailbox.py

@@ -1113,6 +1113,29 @@ class TestMbox(_TestMboxMMDF, unittest.TestCase):
             perms = st.st_mode
             self.assertFalse((perms & 0o111)) # Execute bits should all be off.
 
+    def test_terminating_newline(self):
+        message = email.message.Message()
+        message['From'] = 'john@example.com'
+        message.set_payload('No newline at the end')
+        i = self._box.add(message)
+
+        # A newline should have been appended to the payload
+        message = self._box.get(i)
+        self.assertEqual(message.get_payload(), 'No newline at the end\n')
+
+    def test_message_separator(self):
+        # Check there's always a single blank line after each message
+        self._box.add('From: foo\n\n0')  # No newline at the end
+        with open(self._path) as f:
+            data = f.read()
+            self.assertEqual(data[-3:], '0\n\n')
+
+        self._box.add('From: foo\n\n0\n')  # Newline at the end
+        with open(self._path) as f:
+            data = f.read()
+            self.assertEqual(data[-3:], '0\n\n')
+
+
 class TestMMDF(_TestMboxMMDF, unittest.TestCase):
 
     _factory = lambda self, path, factory=None: mailbox.MMDF(path, factory)