added tests

tests/users/test_api_resources.py

@@ -1,4 +1,5 @@
 import unittest
+import asyncio
 from unittest.mock import patch
 
 from flask import json
@@ -343,6 +344,40 @@ def test_user_registration_with_taken_email(self, send_email_function):
             )
             self.assertEqual(response.status_code, 409)
 
+    @patch("flask_mail._MailMixin.send", side_effect=mail_send_mocked)
+    def test_race_conditions_on_signup(self, send_email_function):
+        async def make_request():
+            user = UserModel.query.first()
+            email = user.email
+            response = self.client.post(
+                "/register",
+                data=json.dumps(
+                    dict(
+                        name=user1["name"],
+                        username=user1["username"],
+                        password=user1["password"],
+                        email=email,
+                        terms_and_conditions_checked=user1[
+                            "terms_and_conditions_checked"
+                        ],
+                    )
+                ),
+                follow_redirects=True,
+                content_type="application/json",
+            )
+            message = json.loads(response.get_data(as_text=True)).get("message")
+            users_count = UserModel.query.filter_by(email=email).count()
+            self.assertEqual(users_count, 1)
+            self.assertEqual(
+                message, USER_USES_AN_EMAIL_ID_THAT_ALREADY_EXISTS.get("message")
+            )
+            self.assertEqual(response.status_code, 409)
+
+        async def make2requests():
+            await asyncio.gather(make_request(), make_request())
+
+        asyncio.run(make2requests())
+
 
 if __name__ == "__main__":
     unittest.main()