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 const Cc = Components.classes;

 const Ci = Components.interfaces;

 var addedTopic = "xpcom-category-entry-added";

 var removedTopic = "xpcom-category-entry-removed";

 var testCategory = "bug-test-category";

 var testEntry = "@mozilla.org/bug-test-entry;1";

 var testValue= "check validity";

 var result = "";

 var expected = "add remove add remove ";

 var timer;

 var observer = {

   QueryInterface: function(iid) {

     if (iid.equals(Ci.nsISupports) || iid.equals(Ci.nsIObserver))

       return this;

     throw Components.results.NS_ERROR_NO_INTERFACE;

   },

   observe: function(subject, topic, data) {

     if (topic == "timer-callback") {

       do_check_eq(result, expected);

       var observerService = Cc["@mozilla.org/observer-service;1"].getService(Ci.nsIObserverService);

       observerService.removeObserver(this, addedTopic);

       observerService.removeObserver(this, removedTopic);

       do_test_finished();

       timer = null;

     }

     if (subject.QueryInterface(Ci.nsISupportsCString).data != testEntry || data != testCategory)

       return;

     if (topic == addedTopic)

       result += "add ";

     else if (topic == removedTopic)

       result += "remove ";

   }

 };

 function run_test() {

   do_test_pending();

   var observerService = Cc["@mozilla.org/observer-service;1"].getService(Ci.nsIObserverService);

   observerService.addObserver(observer, addedTopic, false);

   observerService.addObserver(observer, removedTopic, false);

   var categoryManager = Cc["@mozilla.org/categorymanager;1"].getService(Ci.nsICategoryManager);

   categoryManager.addCategoryEntry(testCategory, testEntry, testValue, false, true);

   categoryManager.addCategoryEntry(testCategory, testEntry, testValue, false, true);

   categoryManager.deleteCategoryEntry(testCategory, testEntry, false);

   timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);

   timer.init(observer, 0, timer.TYPE_ONE_SHOT);

 }