Add test for NullBooleanField with choices

Author: @preston-wagner in PR #6116

tests/test_model_serializer.py

@@ -363,6 +363,27 @@ class TestRegularFieldMappings(TestCase):
 
         ExampleSerializer()
 
+    def test_null_boolean_field_choices(self):
+
+        class Trivial(models.Model):
+            CHECKLIST_OPTIONS = (
+                (None, 'none'),
+                (True, 'checked'),
+                (False, 'N/A'),
+            )
+
+            name = models.CharField(max_length=255)
+            theoretically_nullable_field = models.NullBooleanField(choices=CHECKLIST_OPTIONS)
+
+        class TrivialSerializer(serializers.ModelSerializer):
+            class Meta:
+                model = Trivial
+                fields = '__all__'
+
+        trivial_serialized = TrivialSerializer(data=dict(name='test', theoretically_nullable_field=None))
+        self.assertTrue(trivial_serialized.is_valid())
+        self.assertEqual(trivial_serialized.errors, {})
+
 
 class TestDurationFieldMapping(TestCase):
     def test_duration_field(self):