Add tests for .data access before .is_valid() in relation serializers

- Add test_data_cannot_be_accessed_prior_to_is_valid to HyperlinkedManyToManyTests
- Add test_data_cannot_be_accessed_prior_to_is_valid to PKManyToManyTests
- Remove TODO comments that were addressed
- Ensures AssertionError is raised when accessing .data before validation

Fixes TODO items in:
- tests/test_relations_hyperlink.py (line 71)
- tests/test_relations_pk.py (line 97)

tests/test_relations_hyperlink.py

@@ -1,3 +1,4 @@
+import pytest
 from django.test import TestCase, override_settings
 from django.urls import path
 
@@ -68,7 +69,6 @@ class NullableOneToOneTargetSerializer(serializers.HyperlinkedModelSerializer):
         fields = ('url', 'name', 'nullable_source')
 
 
-# TODO: Add test that .data cannot be accessed prior to .is_valid
 @override_settings(ROOT_URLCONF='tests.test_relations_hyperlink')
 class HyperlinkedManyToManyTests(TestCase):
     def setUp(self):
@@ -193,6 +193,15 @@ class HyperlinkedManyToManyTests(TestCase):
         ]
         assert serializer.data == expected
 
+    def test_data_cannot_be_accessed_prior_to_is_valid(self):
+        """Test that .data cannot be accessed prior to .is_valid for hyperlinked serializers."""
+        serializer = ManyToManySourceSerializer(
+            data={'name': 'test-source', 'targets': ['http://testserver/manytomanytarget/1/']},
+            context={'request': request}
+        )
+        with pytest.raises(AssertionError):
+            serializer.data
+
 
 @override_settings(ROOT_URLCONF='tests.test_relations_hyperlink')
 class HyperlinkedForeignKeyTests(TestCase):

tests/test_relations_pk.py

@@ -1,3 +1,4 @@
+import pytest
 from django.test import TestCase
 
 from rest_framework import serializers
@@ -94,8 +95,6 @@ class OneToOnePKSourceSerializer(serializers.ModelSerializer):
         fields = '__all__'
 
 
-# TODO: Add test that .data cannot be accessed prior to .is_valid
-
 class PKManyToManyTests(TestCase):
     def setUp(self):
         for idx in range(1, 4):
@@ -218,6 +217,14 @@ class PKManyToManyTests(TestCase):
         ]
         assert serializer.data == expected
 
+    def test_data_cannot_be_accessed_prior_to_is_valid(self):
+        """Test that .data cannot be accessed prior to .is_valid for primary key serializers."""
+        serializer = ManyToManySourceSerializer(
+            data={'name': 'test-source', 'targets': [1]}
+        )
+        with pytest.raises(AssertionError):
+            serializer.data
+
 
 class PKForeignKeyTests(TestCase):
     def setUp(self):