Add regression test for DecimalField mapping

tests/test_model_serializer.py

@@ -22,7 +22,7 @@
 
 from rest_framework import serializers
 from rest_framework.compat import DurationField as ModelDurationField
-from rest_framework.compat import unicode_repr
+from rest_framework.compat import DecimalValidator, unicode_repr
 
 
 def dedent(blocktext):
@@ -861,3 +861,41 @@ class Meta:
         }]
 
         assert serializer.data == expected
+
+
+class DecimalFieldModel(models.Model):
+    decimal_field = models.DecimalField(
+        max_digits=3,
+        decimal_places=1,
+        validators=[MinValueValidator(1), MaxValueValidator(3)]
+    )
+
+
+class TestDecimalFieldMappings(TestCase):
+    @pytest.mark.skipif(DecimalValidator is not None,
+                        reason='DecimalValidator is available in Django 1.9+')
+    def test_decimal_field_has_no_decimal_validator(self):
+        """
+        Test that a DecimalField has no validators before Django 1.9.
+        """
+        class TestSerializer(serializers.ModelSerializer):
+            class Meta:
+                model = DecimalFieldModel
+
+        serializer = TestSerializer()
+
+        assert len(serializer.fields['decimal_field'].validators) == 0
+
+    @pytest.mark.skipif(DecimalValidator is None,
+                        reason='DecimalValidator is available in Django 1.9+')
+    def test_decimal_field_has_decimal_validator(self):
+        """
+        Test that a DecimalField has DecimalValidator in Django 1.9+.
+        """
+        class TestSerializer(serializers.ModelSerializer):
+            class Meta:
+                model = DecimalFieldModel
+
+        serializer = TestSerializer()
+
+        assert len(serializer.fields['decimal_field'].validators) == 2