Index: test/filterStorage.js
===================================================================
--- a/test/filterStorage.js
+++ b/test/filterStorage.js
@@ -51,17 +51,17 @@
   let result = FilterStorage.subscriptions.map(
     subscription => subscription.filters.map(
       filter => filter.text));
   test.deepEqual(result, list, testMessage);
 }
 
 function compareFilterSubscriptions(test, testMessage, filter, list)
 {
-  let result = filter.subscriptions.map(subscription => subscription.url);
+  let result = [...filter.subscriptions].map(subscription => subscription.url);
   let expected = list.map(subscription => subscription.url);
   test.deepEqual(result, expected, testMessage);
 }
 
 exports.testAddingSubscriptions = function(test)
 {
   let subscription1 = Subscription.fromURL("http://test1/");
   let subscription2 = Subscription.fromURL("http://test2/");