         dataStack.performInNewBackgroundContext { backgroundContext in
             self.createUsers(context: backgroundContext)
 
-            let before = DataObjectIDs.objectIDs(inEntityNamed: "User", withAttributesNamed: "remoteID", context: backgroundContext)
+            let before = backgroundContext.objectIDs(inEntityNamed: "User", withAttributesNamed: "remoteID")
             let JSONObjects = try! JSON.from("users2.json", bundle: Bundle(for: DataFilterTests.self)) as! [[String: Any]]
             var inserted = 0
             var updated = 0

            self.user(remoteID: 0, firstName: "Amy", lastName: "Juergens", age: 21, context: backgroundContext)
            self.user(remoteID: 1, firstName: "Ben", lastName: "Boykewich", age: 23, context: backgroundContext)

            let before = DataObjectIDs.objectIDs(inEntityNamed: "User", withAttributesNamed: "remoteID", context: backgroundContext)
            let JSONObjects = try! JSON.from("simple.json", bundle: Bundle(for: DataFilterTests.self)) as! [[String: Any]]
            var inserted = 0
            var updated = 0
            var deleted = before.count
            DataFilter.changes(JSONObjects, inEntityNamed: "User", predicate: nil, operations: [.Delete], localPrimaryKey: "remoteID", remotePrimaryKey: "id", context: backgroundContext, inserted: { objectJSON in
                inserted += 1
            }, updated: { objectJSON, updatedObject in
                updated += 1

        dataStack.performInNewBackgroundContext { backgroundContext in
            self.createUsers(context: backgroundContext)

            let before = backgroundContext.objectIDs(inEntityNamed: "User", withAttributesNamed: "remoteID")
            let JSONObjects = try! JSON.from("users-with-nil.json", bundle: Bundle(for: DataFilterTests.self)) as! [[String: Any]]
            var inserted = 0
            var updated = 0
