test(flags): make wrong-key load_feature_flags deterministic (#432)

Author: andehen

posthog/client.py

@@ -1928,10 +1928,12 @@ def _capture_feature_flag_called(
             f"{key}_{'::null::' if response is None else str(response)}"
         )
 
-        if (
-            feature_flag_reported_key
-            not in self.distinct_ids_feature_flags_reported[distinct_id]
-        ):
+        reported_flags = self.distinct_ids_feature_flags_reported.get(distinct_id)
+        if reported_flags is None:
+            reported_flags = set()
+            self.distinct_ids_feature_flags_reported[distinct_id] = reported_flags
+
+        if feature_flag_reported_key not in reported_flags:
             properties: dict[str, Any] = {
                 "$feature_flag": key,
                 "$feature_flag_response": response,
@@ -1967,9 +1969,7 @@ def _capture_feature_flag_called(
                 groups=groups,
                 disable_geoip=disable_geoip,
             )
-            self.distinct_ids_feature_flags_reported[distinct_id].add(
-                feature_flag_reported_key
-            )
+            reported_flags.add(feature_flag_reported_key)
 
     def get_remote_config_payload(self, key: str):
         if self.disabled:

posthog/test/test_feature_flags.py

@@ -2513,7 +2513,10 @@ def test_load_feature_flags_clears_etag_when_server_stops_sending(
         self.assertIsNone(client._flags_etag)
         self.assertEqual(client.feature_flags[0]["key"], "flag-v2")
 
-    def test_load_feature_flags_wrong_key(self):
+    @mock.patch("posthog.client.Poller")
+    @mock.patch("posthog.client.get")
+    def test_load_feature_flags_wrong_key(self, patch_get, _patch_poll):
+        patch_get.side_effect = APIError(401, "Unauthorized")
         client = Client(FAKE_TEST_API_KEY, personal_api_key=FAKE_TEST_API_KEY)
 
         with self.assertLogs("posthog", level="ERROR") as logs:
@@ -4266,13 +4269,15 @@ def test_disable_geoip_get_flag_capture_call(self, patch_flags, patch_capture):
             disable_geoip=False,
         )
 
-    @mock.patch("posthog.client.MAX_DICT_SIZE", 100)
     @mock.patch.object(Client, "capture")
     @mock.patch("posthog.client.flags")
     def test_capture_multiple_users_doesnt_out_of_memory(
         self, patch_flags, patch_capture
     ):
         client = Client(FAKE_TEST_API_KEY, personal_api_key=FAKE_TEST_API_KEY)
+        # Set on the instance to avoid relying on module-constant patching behavior
+        # across Python/runtime implementations.
+        client.distinct_ids_feature_flags_reported.max_size = 100
         client.feature_flags = [
             {
                 "id": 1,