UPDATE

crop_simulation/tests.py

@@ -12,6 +12,7 @@ from rest_framework.test import APIRequestFactory
 
 from .models import SimulationRun, SimulationScenario
 from farm_data.models import PlantCatalogSnapshot, SensorData
+from farm_data.services import assign_farm_plants_from_backend_ids
 from irrigation.models import IrrigationMethod
 from location_data.models import SoilLocation
 from weather.models import WeatherForecast
@@ -393,7 +394,7 @@ class CropSimulationCanonicalSnapshotTests(TestCase):
             weather_forecast=self.weather,
             irrigation_method=self.irrigation_method,
         )
-        self.farm.plants.add(self.plant)
+        assign_farm_plants_from_backend_ids(self.farm, [self.plant.backend_plant_id])
 
     @patch("crop_simulation.services.build_ai_farm_snapshot")
     def test_build_simulation_payload_from_farm_uses_aggregated_metrics(self, mock_snapshot):