Add tests for retrieving/updating reverse fks

rest_framework/tests/nested_relations.py

+from copy import deepcopy
+from django.db import models
+from django.test import TestCase
+from rest_framework import serializers
+
+
+# ForeignKey
+
+class ForeignKeyTarget(models.Model):
+    name = models.CharField(max_length=100)
+
+
+class ForeignKeySource(models.Model):
+    name = models.CharField(max_length=100)
+    target = models.ForeignKey(ForeignKeyTarget, related_name='sources')
+
+
+class ForeignKeySourceSerializer(serializers.ModelSerializer):
+    class Meta:
+        model = ForeignKeySource
+
+
+class ForeignKeyTargetSerializer(serializers.ModelSerializer):
+    sources = ForeignKeySourceSerializer()
+
+    class Meta:
+        model = ForeignKeyTarget
+
+
+class ReverseForeignKeyTests(TestCase):
+    def setUp(self):
+        target = ForeignKeyTarget(name='target-1')
+        target.save()
+        new_target = ForeignKeyTarget(name='target-2')
+        new_target.save()
+        for idx in range(1, 4):
+            source = ForeignKeySource(name='source-%d' % idx, target=target)
+            source.save()
+        self.target_data = {'id': 1, 'name': u'target-1', 'sources': [
+                {'id': 1, 'name': u'source-1', 'target': 1},
+                {'id': 2, 'name': u'source-2', 'target': 1},
+                {'id': 3, 'name': u'source-3', 'target': 1},
+            ]}
+        self.new_target_data = {'id': 2, 'name': u'target-2', 'sources': []}
+        self.data = [self.target_data, self.new_target_data]
+
+    def test_reverse_foreign_key_retrieve(self):
+        queryset = ForeignKeyTarget.objects.all()
+        serializer = ForeignKeyTargetSerializer(queryset)
+        self.assertEquals(serializer.data, self.data)
+
+    def test_reverse_foreign_key_update(self):
+        data = deepcopy(self.target_data)
+        data['sources'][0]['name'] = 'source-1-changed'
+        data['sources'][2]['name'] = 'source-3-changed'
+        instance = ForeignKeyTarget.objects.get(pk=1)
+        serializer = ForeignKeyTargetSerializer(instance, data=data)
+        self.assertTrue(serializer.is_valid())
+        self.assertEquals(serializer.data, data)
+        serializer.save()
+
+        # Ensure target 1 is updated, and everything else is as expected
+        queryset = ForeignKeyTarget.objects.all()
+        serializer = ForeignKeyTargetSerializer(queryset)
+        expected = deepcopy(self.data)
+        expected[0]['sources'][0]['name'] = 'source-1-changed'
+        expected[0]['sources'][2]['name'] = 'source-3-changed'
+        self.assertEquals(serializer.data, expected)