Index: test/filterListener.js
===================================================================
--- a/test/filterListener.js
+++ b/test/filterListener.js
@@ -292,28 +292,28 @@
   checkKnownFilters(test, "enable blocking filters", {blacklist: [filter1.text]});
 
   let subscription3 = Subscription.fromURL("~wl~");
   subscription3.disabled = true;
   checkKnownFilters(test, "disable exception rules", {blacklist: [filter1.text]});
 
   FilterStorage.addFilter(filter2);
   checkKnownFilters(test, "add @@filter2", {blacklist: [filter1.text], whitelist: [filter2.text]});
-  test.equal(filter2.subscriptions.length, 1, "@@filter2.subscription.length");
-  test.ok(filter2.subscriptions[0] instanceof SpecialSubscription, "@@filter2 added to a new filter group");
-  test.ok(filter2.subscriptions[0] != subscription3, "@@filter2 filter group is not the disabled exceptions group");
+  test.equal(filter2.subscriptions.size, 1, "@@filter2.subscription.length");
+  test.ok([...filter2.subscriptions][0] instanceof SpecialSubscription, "@@filter2 added to a new filter group");
+  test.ok([...filter2.subscriptions][0] != subscription3, "@@filter2 filter group is not the disabled exceptions group");
 
   subscription3.disabled = false;
   checkKnownFilters(test, "enable exception rules", {blacklist: [filter1.text], whitelist: [filter2.text]});
 
   FilterStorage.removeFilter(filter2);
   FilterStorage.addFilter(filter2);
   checkKnownFilters(test, "re-add @@filter2", {blacklist: [filter1.text], whitelist: [filter2.text]});
-  test.equal(filter2.subscriptions.length, 1, "@@filter2.subscription.length");
-  test.ok(filter2.subscriptions[0] == subscription3, "@@filter2 added to the default exceptions group");
+  test.equal(filter2.subscriptions.size, 1, "@@filter2.subscription.length");
+  test.ok([...filter2.subscriptions][0] == subscription3, "@@filter2 added to the default exceptions group");
 
   let subscription4 = Subscription.fromURL("http://test/");
   FilterStorage.updateSubscriptionFilters(subscription4, [filter3, filter4, filter5]);
   checkKnownFilters(test, "update subscription not in the list yet", {blacklist: [filter1.text], whitelist: [filter2.text]});
 
   FilterStorage.addSubscription(subscription4);
   checkKnownFilters(test, "add subscription to the list", {blacklist: [filter1.text, filter3.text], whitelist: [filter2.text, filter4.text]});