fixup

mail/tests/test_celery_tasks.py

@@ -1,4 +1,6 @@
+import concurrent.futures
 import email.mime.multipart
+import time
 from datetime import datetime, timezone
 from email.mime.multipart import MIMEMultipart
 from smtplib import SMTPException
@@ -294,3 +296,50 @@ def test_sends_email_max_retry_failures(self, exception_class, mock_get_smtp_con
         )
         self.assertEqual(mock_conn.quit.call_count, MAX_RETRIES + 1)
         mock_cache.lock.assert_called_with("global_send_email_lock", timeout=600)
+
+    @mock.patch("mail.servers.get_smtp_connection")
+    def test_locking(self, mock_get_smtp_connection):
+        results = []
+
+        def _sleepy(message):
+            call = {}
+            call["start"] = {
+                "message": message,
+                "time": time.monotonic(),
+            }
+            time.sleep(1)
+            call["end"] = {
+                "message": message,
+                "time": time.monotonic(),
+            }
+            results.append(call)
+
+        mock_conn = mock_get_smtp_connection()
+        mock_conn.send_message.side_effect = _sleepy
+
+        with concurrent.futures.ThreadPoolExecutor() as executor:
+            message_1 = {
+                "From": "[email protected]",
+                "To": "[email protected]",
+            }
+            future_1 = executor.submit(send_email_task.apply, args=[message_1])
+
+            message_2 = {
+                "From": "[email protected]",
+                "To": "[email protected]",
+            }
+            future_2 = executor.submit(send_email_task.apply, args=[message_2])
+
+        future_1.result()
+        future_2.result()
+
+        first_call, second_call = results
+
+        assert first_call["start"]["message"] == {"From": "[email protected]", "To": "[email protected]"}
+        assert first_call["end"]["message"] == {"From": "[email protected]", "To": "[email protected]"}
+
+        assert second_call["start"]["message"] == {"From": "[email protected]", "To": "[email protected]"}
+        assert second_call["end"]["message"] == {"From": "[email protected]", "To": "[email protected]"}
+
+        assert second_call["start"]["time"] > first_call["end"]["time"]
+        assert second_call["start"]["time"] > first_call["start"]["time"] + 1