Add plan variety change tracking

backend/apps/plans/tests.py

@@ -1,3 +1,92 @@
+from django.contrib.auth import get_user_model
 from django.test import TestCase
+from rest_framework.test import APIRequestFactory, force_authenticate
 
-# Create your tests here.
+from apps.fields.models import Field
+from .models import Crop, Plan, PlanVarietyChange, Variety
+from .serializers import PlanSerializer
+from .views import PlanViewSet
+
+
+class PlanVarietyChangeTests(TestCase):
+    def setUp(self):
+        self.factory = APIRequestFactory()
+        self.user = get_user_model().objects.create_user(
+            username='tester',
+            password='secret12345',
+        )
+        self.crop = Crop.objects.create(name='水稲')
+        self.old_variety = Variety.objects.create(crop=self.crop, name='にこまる')
+        self.new_variety = Variety.objects.create(crop=self.crop, name='たちはるか特栽')
+        self.field = Field.objects.create(
+            name='足川北上',
+            address='高知県高岡郡',
+            area_tan='1.2000',
+            area_m2=1200,
+            owner_name='吉田',
+            group_name='北',
+            display_order=1,
+        )
+        self.plan = Plan.objects.create(
+            field=self.field,
+            year=2026,
+            crop=self.crop,
+            variety=self.old_variety,
+            notes='',
+        )
+
+    def test_serializer_update_creates_history_when_variety_changes(self):
+        serializer = PlanSerializer(
+            instance=self.plan,
+            data={'variety': self.new_variety.id},
+            partial=True,
+        )
+        self.assertTrue(serializer.is_valid(), serializer.errors)
+        serializer.save()
+
+        self.plan.refresh_from_db()
+        self.assertEqual(self.plan.variety_id, self.new_variety.id)
+
+        change = PlanVarietyChange.objects.get(plan=self.plan)
+        self.assertEqual(change.field_id, self.field.id)
+        self.assertEqual(change.year, 2026)
+        self.assertEqual(change.old_variety_id, self.old_variety.id)
+        self.assertEqual(change.new_variety_id, self.new_variety.id)
+        self.assertEqual(change.moved_entry_count, 0)
+
+    def test_serializer_update_does_not_create_history_without_variety_change(self):
+        serializer = PlanSerializer(
+            instance=self.plan,
+            data={'notes': 'メモ更新'},
+            partial=True,
+        )
+        self.assertTrue(serializer.is_valid(), serializer.errors)
+        serializer.save()
+
+        self.plan.refresh_from_db()
+        self.assertEqual(self.plan.notes, 'メモ更新')
+        self.assertFalse(PlanVarietyChange.objects.exists())
+
+    def test_bulk_update_creates_history_for_existing_plan(self):
+        view = PlanViewSet.as_view({'post': 'bulk_update'})
+        request = self.factory.post(
+            '/api/plans/bulk_update/',
+            {
+                'field_ids': [self.field.id],
+                'year': 2026,
+                'crop': self.crop.id,
+                'variety': self.new_variety.id,
+            },
+            format='json',
+        )
+        force_authenticate(request, user=self.user)
+
+        response = view(request)
+
+        self.assertEqual(response.status_code, 200)
+        self.plan.refresh_from_db()
+        self.assertEqual(self.plan.variety_id, self.new_variety.id)
+
+        change = PlanVarietyChange.objects.get(plan=self.plan)
+        self.assertEqual(change.old_variety_id, self.old_variety.id)
+        self.assertEqual(change.new_variety_id, self.new_variety.id)