Update mock endpoints for the custom objects

When creating a custom object which already exists we update the value
and increment the version

Author: mvantellingen

src/commercetools/testing/custom_objects.py

@@ -20,6 +20,27 @@ class CustomObjectsModel(BaseModel):
     def _generate_key(self, obj):
         return obj.container, obj.key
 
+    def add(self, draft, id=None):
+        """Add a new object to the storage.
+
+        If the container/key already exists we update the value as long as the
+        version matches. otherwise create a new item
+        """
+        new_obj = self._create_from_draft(draft, id)
+        current_obj = self._get_by_container_key(new_obj.container, new_obj.key)
+
+        if current_obj:
+            if current_obj["version"] != new_obj.version:
+                raise ValueError(
+                    "Version mismatch: got %d, expected %d"
+                    % (new_obj.version, current_obj["version"])
+                )
+            current_obj["value"] = new_obj.value
+            self.save(current_obj)
+            return current_obj
+        else:
+            return self._store_obj(new_obj)
+
     def _create_from_draft(
         self, obj: types.CustomObjectDraft, id: typing.Optional[str] = None
     ) -> types.CustomObject:
@@ -34,6 +55,18 @@ def _create_from_draft(
             last_modified_at=datetime.datetime.now(datetime.timezone.utc),
         )
 
+    def _get_by_container_key(
+        self, container: str, key: str
+    ) -> typing.Optional[typing.Dict]:
+        return next(
+            (
+                obj
+                for obj in self.objects.values()
+                if obj["container"] == container and obj["key"] == key
+            ),
+            None,
+        )
+
 
 class CustomObjectsBackend(ServiceBackend):
     service_path = "custom-objects"
@@ -59,14 +92,7 @@ def query_by_container(self, request, container: str):
         return self.query(request)
 
     def get_by_container_key(self, request, container: str, key: str):
-        item = next(
-            (
-                obj
-                for obj in self.model.objects.values()
-                if obj["container"] == container and obj["key"] == key
-            ),
-            None,
-        )
+        item = self.model._get_by_container_key(container, key)
         if item:
             return create_commercetools_response(request, json=item)
         else: