From 5cbdfaed9eaaf61e7cc9e75a3ff4b7c3965c087f Mon Sep 17 00:00:00 2001
From: Tom Christie <tom@tomchristie.com>
Date: Tue, 2 Aug 2016 12:37:08 +0100
Subject: [PATCH] Serializer default= values should not be included in updates

---
 tests/test_serializer.py | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/tests/test_serializer.py b/tests/test_serializer.py
index 741c6ab17..4877de93b 100644
--- a/tests/test_serializer.py
+++ b/tests/test_serializer.py
@@ -309,3 +309,31 @@ class TestCacheSerializerData:
         pickled = pickle.dumps(serializer.data)
         data = pickle.loads(pickled)
         assert data == {'field1': 'a', 'field2': 'b'}
+
+
+class TestDefaultInclusions:
+    def setup(self):
+        class ExampleSerializer(serializers.Serializer):
+            char = serializers.CharField(read_only=True, default='abc')
+            integer = serializers.IntegerField()
+        self.Serializer = ExampleSerializer
+
+    def test_default_should_included_on_create(self):
+        serializer = self.Serializer(data={'integer': 456})
+        assert serializer.is_valid()
+        assert serializer.validated_data == {'char': 'abc', 'integer': 456}
+        assert serializer.errors == {}
+
+    def test_default_should_not_be_included_on_update(self):
+        instance = MockObject(char='def', integer=123)
+        serializer = self.Serializer(instance, data={'integer': 456})
+        assert serializer.is_valid()
+        assert serializer.validated_data == {'integer': 456}
+        assert serializer.errors == {}
+
+    def test_default_should_not_be_included_on_partial_update(self):
+        instance = MockObject(char='def', integer=123)
+        serializer = self.Serializer(instance, data={'integer': 456}, partial=True)
+        assert serializer.is_valid()
+        assert serializer.validated_data == {'integer': 456}
+        assert serializer.errors == {}