--- a/toolkit/components/url-classifier/tests/mochitest/classifierCommon.js
+++ b/toolkit/components/url-classifier/tests/mochitest/classifierCommon.js
@@ -14,17 +14,17 @@ function doUpdate(update) {
       throw Cr.NS_ERROR_NO_INTERFACE;
     },
     updateUrlRequested: function(url) { },
     streamFinished: function(status) { },
     updateError: function(errorCode) {
       sendAsyncMessage("updateError", { errorCode });
     },
     updateSuccess: function(requestedTimeout) {
-      sendAsyncMessage("loadTestFrame");
+      sendAsyncMessage("updateSuccess");
     }
   };
 
   let dbService = Cc["@mozilla.org/url-classifier/dbservice;1"]
                   .getService(Ci.nsIUrlClassifierDBService);
 
   dbService.beginUpdate(listener, "test-malware-simple,test-unwanted-simple", "");
   dbService.beginStream("", "");

new file mode 100644
--- /dev/null
+++ b/toolkit/components/url-classifier/tests/mochitest/classifierHelper.js
@@ -0,0 +1,100 @@
+if (typeof(classifierHelper) == "undefined") {
+  var classifierHelper = {};
+}
+
+const CLASSIFIER_COMMON_URL = SimpleTest.getTestFileURL("classifierCommon.js");
+var classifierCommonScript = SpecialPowers.loadChromeScript(CLASSIFIER_COMMON_URL);
+
+// addUrlToDB & removeUrlFromDB are asynchronous, queue the task to ensure
+// the callback follow correct order.
+classifierHelper._updates = [];
+
+// Keep urls added to database, those urls should be automatically
+// removed after test complete.
+classifierHelper._updatesToCleanup = [];
+
+// Pass { url: ..., db: ... } to add url to database,
+// onsuccess/onerror will be called when update complete.
+classifierHelper.addUrlToDB = function(updateData, onsuccess, onerror) {
+  var testUpdate = "";
+  for (var update of updateData) {
+    classifierHelper._updatesToCleanup.push(update);
+    testUpdate +=
+      "n:1000\ni:" + update.db + "\nad:1\n" +
+      "a:524:32:" + update.url.length + "\n" +
+      update.url;
+  }
+
+  classifierHelper._update(testUpdate, onsuccess, onerror);
+}
+
+// Pass { url: ..., db: ... } to remove url from database,
+// onsuccess/onerror will be called when update complete.
+classifierHelper.removeUrlFromDB = function(updateData, onsuccess, onerror) {
+  var testUpdate = "";
+  for (var update of updateData) {
+    testUpdate +=
+      "n:1000\ni:" + update.db + "\nsd:1\n" +
+      "s:524:32:" + (4 + update.url.length) + "\n" +
+      "524:" + update.url;
+  }
+
+  classifierHelper._updatesToCleanup =
+    classifierHelper._updatesToCleanup.filter((v) => {
+      return updateData.indexOf(v) == -1;
+    });
+
+  classifierHelper._update(testUpdate, onsuccess, onerror);
+};
+
+classifierHelper._update = function(testUpdate, onsuccess, onerror) {
+  // Queue the task if there is still an on-going update
+  classifierHelper._updates.push({"data": testUpdate,
+                                  "onsuccess": onsuccess,
+                                  "onerror": onerror});
+  if (classifierHelper._updates.length != 1) {
+    return;
+  }
+
+  classifierCommonScript.sendAsyncMessage("doUpdate", { testUpdate });
+};
+
+classifierHelper._updateSuccess = function() {
+  var update = classifierHelper._updates.shift();
+  update.onsuccess();
+
+  if (classifierHelper._updates.length) {
+    var testUpdate = classifierHelper._updates[0].data;
+    classifierCommonScript.sendAsyncMessage("doUpdate", { testUpdate });
+  }
+};
+
+classifierHelper._updateError = function(errorCode) {
+  var update = classifierHelper._updates.shift();
+  update.onerror(errorCode);
+
+  if (classifierHelper._updates.length) {
+    var testUpdate = classifierHelper._updates[0].data;
+    classifierCommonScript.sendAsyncMessage("doUpdate", { testUpdate });
+  }
+};
+
+classifierHelper._setup = function() {
+  classifierCommonScript.addMessageListener("updateSuccess", classifierHelper._updateSuccess);
+  classifierCommonScript.addMessageListener("updateError", classifierHelper._updateError);
+
+  // cleanup will be called at end of each testcase to remove all the urls added to database.
+  SimpleTest.registerCleanupFunction(classifierHelper._cleanup);
+};
+
+classifierHelper._cleanup = function() {
+  if (!classifierHelper._updatesToCleanup) {
+    return Promise.resolve();
+  }
+
+  return new Promise(function(resolve, reject) {
+    classifierHelper.removeUrlFromDB(classifierHelper._updatesToCleanup, resolve, reject);
+  });
+};
+
+classifierHelper._setup();

--- a/toolkit/components/url-classifier/tests/mochitest/mochitest.ini
+++ b/toolkit/components/url-classifier/tests/mochitest/mochitest.ini
@@ -1,14 +1,15 @@
 [DEFAULT]
 skip-if = buildapp == 'b2g'
 support-files =
   classifiedAnnotatedPBFrame.html
   classifierCommon.js
   classifierFrame.html
+  classifierHelper.js
   cleanWorker.js
   good.js
   evil.css
   evil.js
   evil.js^headers^
   evilWorker.js
   import.css
   raptor.jpg

--- a/toolkit/components/url-classifier/tests/mochitest/test_classifier.html
+++ b/toolkit/components/url-classifier/tests/mochitest/test_classifier.html
@@ -1,64 +1,60 @@
 <!DOCTYPE HTML>
 <html>
 <head>
   <title>Test the URI Classifier</title>
   <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="classifierHelper.js"></script>
   <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
 </head>
 
 <p id="display"></p>
 <div id="content" style="display: none">
 </div>
 <pre id="test">
 
 <script class="testbody" type="text/javascript">
 
 var firstLoad = true;
 
 // Add some URLs to the malware database.
-var testData = "malware.example.com/";
-var testUpdate =
-  "n:1000\ni:test-malware-simple\nad:1\n" +
-  "a:524:32:" + testData.length + "\n" +
-  testData;
-
-testData = "unwanted.example.com/";
-testUpdate +=
-  "n:1000\ni:test-unwanted-simple\nad:1\n" +
-  "a:524:32:" + testData.length + "\n" +
-  testData;
+var testData = [
+  { url: "malware.example.com/",
+    db: "test-malware-simple"
+  },
+  { url: "unwanted.example.com/",
+    db: "test-unwanted-simple"
+  }
+];
 
 function loadTestFrame() {
   document.getElementById("testFrame").src = "classifierFrame.html";
 }
 
-const CLASSIFIER_COMMON_URL = SimpleTest.getTestFileURL("classifierCommon.js");
-let classifierCommonScript = SpecialPowers.loadChromeScript(CLASSIFIER_COMMON_URL);
-
 // Expected finish() call is in "classifierFrame.html".
 SimpleTest.waitForExplicitFinish();
 
-classifierCommonScript.addMessageListener("loadTestFrame", () => {
+function updateSuccess() {
   SpecialPowers.pushPrefEnv(
     {"set" : [["browser.safebrowsing.malware.enabled", true]]},
     loadTestFrame);
-});
-classifierCommonScript.addMessageListener("updateError", ({ errorCode }) => {
+}
+
+function updateError(errorCode) {
   ok(false, "Couldn't update classifier. Error code: " + errorCode);
   // Abort test.
   SimpleTest.finish();
-});
+}
 
 SpecialPowers.pushPrefEnv(
   {"set" : [["urlclassifier.malwareTable", "test-malware-simple,test-unwanted-simple"],
             ["urlclassifier.phishTable", "test-phish-simple"]]},
   function() {
-    classifierCommonScript.sendAsyncMessage("doUpdate", { testUpdate });
+    classifierHelper.addUrlToDB(testData, updateSuccess, updateError);
   });
 
 </script>
 
 </pre>
 <iframe id="testFrame" onload=""></iframe>
 </body>
 </html>

--- a/toolkit/components/url-classifier/tests/mochitest/test_classifier_worker.html
+++ b/toolkit/components/url-classifier/tests/mochitest/test_classifier_worker.html
@@ -1,35 +1,33 @@
 <!DOCTYPE HTML>
 <html>
 <head>
   <title>Test the URI Classifier</title>
   <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="classifierHelper.js"></script>
   <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
 </head>
 
 <p id="display"></p>
 <div id="content" style="display: none">
 </div>
 <pre id="test">
 
 <script class="testbody" type="text/javascript">
 
 // Add some URLs to the malware database.
-var testData = "example.com/tests/toolkit/components/url-classifier/tests/mochitest/evilWorker.js";
-var testUpdate =
-  "n:1000\ni:test-malware-simple\nad:550\n" +
-  "a:550:32:" + testData.length + "\n" +
-  testData;
-
-testData = "example.com/tests/toolkit/components/url-classifier/tests/mochitest/unwantedWorker.js";
-testUpdate +=
-  "n:1000\ni:test-unwanted-simple\nad:550\n" +
-  "a:550:32:" + testData.length + "\n" +
-  testData;
+var testData = [
+  { url: "example.com/tests/toolkit/components/url-classifier/tests/mochitest/evilWorker.js",
+    db: "test-malware-simple"
+  },
+  { url: "example.com/tests/toolkit/components/url-classifier/tests/mochitest/unwantedWorker.js",
+    db: "test-unwanted-simple"
+  }
+];
 
 function loadTestFrame() {
   document.getElementById("testFrame").src =
     "http://example.com/tests/toolkit/components/url-classifier/tests/mochitest/workerFrame.html";
 }
 
 function onmessage(event)
 {
@@ -37,35 +35,33 @@ function onmessage(event)
   if (pieces[0] == "finish") {
     SimpleTest.finish();
     return;
   }
 
   is(pieces[0], "success", pieces[1]);
 }
 
-const CLASSIFIER_COMMON_URL = SimpleTest.getTestFileURL("classifierCommon.js");
-let classifierCommonScript = SpecialPowers.loadChromeScript(CLASSIFIER_COMMON_URL);
-
-classifierCommonScript.addMessageListener("loadTestFrame", () => {
+function updateSuccess() {
   SpecialPowers.pushPrefEnv(
     {"set" : [["browser.safebrowsing.malware.enabled", true]]},
     loadTestFrame);
-});
-classifierCommonScript.addMessageListener("updateError", ({ errorCode }) => {
+}
+
+function updateError(errorCode) {
   ok(false, "Couldn't update classifier. Error code: " + errorCode);
   // Abort test.
   SimpleTest.finish();
-});
+};
 
 SpecialPowers.pushPrefEnv(
   {"set" : [["urlclassifier.malwareTable", "test-malware-simple,test-unwanted-simple"],
             ["urlclassifier.phishTable", "test-phish-simple"]]},
   function() {
-    classifierCommonScript.sendAsyncMessage("doUpdate", { testUpdate });
+    classifierHelper.addUrlToDB(testData, updateSuccess, updateError);
   });
 
 window.addEventListener("message", onmessage, false);
 
 SimpleTest.waitForExplicitFinish();
 
 </script>