add test for serializer method field

graphene_django/rest_framework/models.py

@@ -9,3 +9,8 @@ class MyFakeModel(models.Model):
 class MyFakeModelWithPassword(models.Model):
     cool_name = models.CharField(max_length=50)
     password = models.CharField(max_length=50)
+
+
+class MyFakeModelWithDate(models.Model):
+    cool_name = models.CharField(max_length=50)
+    last_edited = models.DateField()

graphene_django/rest_framework/tests/test_mutation.py

@@ -8,7 +8,7 @@ from graphene.types.inputobjecttype import InputObjectType
 
 from ...settings import graphene_settings
 from ...types import DjangoObjectType
-from ..models import MyFakeModel, MyFakeModelWithPassword
+from ..models import MyFakeModel, MyFakeModelWithPassword, MyFakeModelWithDate
 from ..mutation import SerializerMutation
 
 
@@ -33,6 +33,18 @@ class MyModelSerializer(serializers.ModelSerializer):
         fields = "__all__"
 
 
+class MyModelSerializerWithMethod(serializers.ModelSerializer):
+    days_since_last_edit = serializers.SerializerMethodField()
+
+    class Meta:
+        model = MyFakeModelWithDate
+        fields = "__all__"
+
+    def get_days_since_last_edit(self, obj):
+        now = datetime.date.fromisoformat("2020-01-08")
+        return (now - obj.last_edited).days
+
+
 class MyModelMutation(SerializerMutation):
     class Meta:
         serializer_class = MyModelSerializer
@@ -208,6 +220,26 @@ def test_model_invalid_update_mutate_and_get_payload_success():
     assert '"id" required' in str(exc.value)
 
 
+@mark.django_db
+def test_perform_mutate_success():
+    class MyMethodMutation(SerializerMutation):
+        class Meta:
+            serializer_class = MyModelSerializerWithMethod
+
+    result = MyMethodMutation.mutate_and_get_payload(
+        None,
+        mock_info(),
+        **{
+            "cool_name": "Narf",
+            "last_edited": datetime.date.fromisoformat("2020-01-04"),
+        }
+    )
+
+    assert result.errors is None
+    assert result.cool_name == "Narf"
+    assert result.days_since_last_edit == 4
+
+
 def test_mutate_and_get_payload_error():
     class MyMutation(SerializerMutation):
         class Meta: