diff --git a/dom/workers/test/Makefile.in b/dom/workers/test/Makefile.in
index e55f944c9ef..ceb83c5aa2e 100644
--- a/dom/workers/test/Makefile.in
+++ b/dom/workers/test/Makefile.in
@@ -145,6 +145,7 @@ _CHROME_TEST_FILES = \
   chromeWorker_subworker.js \
   test_workersDisabled.xul \
   workersDisabled_worker.js \
+  dom_worker_helper.js \
   $(NULL)
 
 ifneq ($(OS_ARCH),WINNT)
diff --git a/dom/workers/test/dom_worker_helper.js b/dom/workers/test/dom_worker_helper.js
new file mode 100644
index 00000000000..d53ffa0596b
--- /dev/null
+++ b/dom/workers/test/dom_worker_helper.js
@@ -0,0 +1,21 @@
+/**
+ * Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+var gRemainingTests = 0;
+
+function waitForWorkerFinish() {
+  if (gRemainingTests == 0) {
+    SimpleTest.waitForExplicitFinish();
+  }
+  ++gRemainingTests;
+}
+
+function finish() {
+  --gRemainingTests;
+  if (gRemainingTests == 0) {
+    SimpleTest.finish();
+  }
+}
+
diff --git a/dom/workers/test/test_chromeWorker.xul b/dom/workers/test/test_chromeWorker.xul
index 3281e503414..35df768beb5 100644
--- a/dom/workers/test/test_chromeWorker.xul
+++ b/dom/workers/test/test_chromeWorker.xul
@@ -11,23 +11,24 @@
           src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"/>
   <script type="application/javascript"
           src="chrome://mochikit/content/tests/SimpleTest/EventUtils.js"/>
+  <script type="application/javascript" src="dom_worker_helper.js"/>
 
   <script type="application/javascript">
   <![CDATA[
 
     function test()
     {
-      SimpleTest.waitForExplicitFinish();
+      waitForWorkerFinish();
 
       var worker = new ChromeWorker("chromeWorker_worker.js");
       worker.onmessage = function(event) {
         is(event.data, "Done!", "Wrong message!");
-        SimpleTest.finish();
+        finish();
       }
       worker.onerror = function(event) {
         ok(false, "Worker had an error: " + event.message);
         worker.terminate();
-        SimpleTest.finish();
+        finish();
       }
       worker.postMessage("go");
     }
diff --git a/dom/workers/test/test_chromeWorkerJSM.xul b/dom/workers/test/test_chromeWorkerJSM.xul
index 66de0ba65e7..01a88bc2a03 100644
--- a/dom/workers/test/test_chromeWorkerJSM.xul
+++ b/dom/workers/test/test_chromeWorkerJSM.xul
@@ -11,20 +11,21 @@
           src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"/>
   <script type="application/javascript"
           src="chrome://mochikit/content/tests/SimpleTest/EventUtils.js"/>
+  <script type="application/javascript" src="dom_worker_helper.js"/>
 
   <script type="application/javascript">
   <![CDATA[
 
     function test()
     {
-      SimpleTest.waitForExplicitFinish();
+      waitForWorkerFinish();
 
       var worker;
 
       function done()
       {
         worker = null;
-        SimpleTest.finish();
+        finish();
       }
 
       function messageCallback(event) {
diff --git a/dom/workers/test/test_file.xul b/dom/workers/test/test_file.xul
index a229d2f7faa..f5c31e06d4a 100644
--- a/dom/workers/test/test_file.xul
+++ b/dom/workers/test/test_file.xul
@@ -6,10 +6,9 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=123456
 -->
 <window title="Mozilla Bug 123456"
         xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
-  <script type="application/javascript"
-          src="chrome://mochikit/content/MochiKit/packed.js"/>
   <script type="application/javascript"
           src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"/>
+  <script type="application/javascript" src="dom_worker_helper.js"/>
 
   <!-- test results are displayed in the html:body -->
   <body xmlns="http://www.w3.org/1999/xhtml">
@@ -57,11 +56,13 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=123456
    * Create a worker to access file properties.
    */
   function accessFileProperties(file, expectedSize, expectedType) {
+    waitForWorkerFinish();
+
     var worker = new Worker("file_worker.js");
 
     worker.onerror = function(event) {
       ok(false, "Worker had an error: " + event.data);
-      SimpleTest.finish();
+      finish();
     };
 
     worker.onmessage = function(event) {
@@ -69,11 +70,10 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=123456
       is(event.data.type, expectedType, "type proproperty accessed from worker is incorrect.");
       is(event.data.name, file.name, "name proproperty accessed from worker is incorrect.");
       is(event.data.mozFullPath, file.mozFullPath, "mozFullPath proproperty accessed from worker is not the same as on main thread.");
-      SimpleTest.finish();
+      finish();
     };
 
     worker.postMessage(file);
-    SimpleTest.waitForExplicitFinish();
   }
 
   // Empty file.
diff --git a/dom/workers/test/test_fileBlobPosting.xul b/dom/workers/test/test_fileBlobPosting.xul
index 66dfed5f98c..c849f026159 100644
--- a/dom/workers/test/test_fileBlobPosting.xul
+++ b/dom/workers/test/test_fileBlobPosting.xul
@@ -6,10 +6,9 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=664783
 -->
 <window title="Mozilla Bug 664783"
         xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
-  <script type="application/javascript"
-          src="chrome://mochikit/content/MochiKit/packed.js"/>
   <script type="application/javascript"
           src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"/>
+  <script type="application/javascript" src="dom_worker_helper.js"/>
 
   <!-- test results are displayed in the html:body -->
   <body xmlns="http://www.w3.org/1999/xhtml">
@@ -62,18 +61,18 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=664783
 
     worker.onerror = function(event) {
       ok(false, "Worker had an error: " + event.data);
-      SimpleTest.finish();
+      finish();
     };
 
     worker.onmessage = function(event) {
       console.log(event.data);
       is(event.data.size, file.size, "size of file posted from worker does not match file posted to worker.");
-      SimpleTest.finish();
+      finish();
     };
 
     var blob = file.mozSlice();
     worker.postMessage(blob);
-    SimpleTest.waitForExplicitFinish();
+    waitForWorkerFinish();
   }
 
   // Empty file.
diff --git a/dom/workers/test/test_fileBlobSubWorker.xul b/dom/workers/test/test_fileBlobSubWorker.xul
index 662b06966e1..d2cf4e113e5 100644
--- a/dom/workers/test/test_fileBlobSubWorker.xul
+++ b/dom/workers/test/test_fileBlobSubWorker.xul
@@ -6,10 +6,9 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=664783
 -->
 <window title="Mozilla Bug 664783"
         xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
-  <script type="application/javascript"
-          src="chrome://mochikit/content/MochiKit/packed.js"/>
   <script type="application/javascript"
           src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"/>
+  <script type="application/javascript" src="dom_worker_helper.js"/>
 
   <!-- test results are displayed in the html:body -->
   <body xmlns="http://www.w3.org/1999/xhtml">
@@ -61,7 +60,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=664783
 
     worker.onerror = function(event) {
       ok(false, "Worker had an error: " + event.data);
-      SimpleTest.finish();
+      finish();
     };
 
     worker.onmessage = function(event) {
@@ -70,12 +69,12 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=664783
       } else {
         is(event.data.size, expectedSize, "size proproperty accessed from worker is not the same as on main thread.");
       }
-      SimpleTest.finish();
+      finish();
     };
 
     var blob = file.mozSlice();
     worker.postMessage(blob);
-    SimpleTest.waitForExplicitFinish();
+    waitForWorkerFinish();
   }
 
   // Empty file.
diff --git a/dom/workers/test/test_fileMozSlice.xul b/dom/workers/test/test_fileMozSlice.xul
index 47872f4ee3a..05240b03d83 100644
--- a/dom/workers/test/test_fileMozSlice.xul
+++ b/dom/workers/test/test_fileMozSlice.xul
@@ -6,10 +6,9 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=664783
 -->
 <window title="Mozilla Bug 664783"
         xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
-  <script type="application/javascript"
-          src="chrome://mochikit/content/MochiKit/packed.js"/>
   <script type="application/javascript"
           src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"/>
+  <script type="application/javascript" src="dom_worker_helper.js"/>
 
   <!-- test results are displayed in the html:body -->
   <body xmlns="http://www.w3.org/1999/xhtml">
@@ -62,18 +61,18 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=664783
 
     worker.onerror = function(event) {
       ok(false, "Worker had an error: " + event.data);
-      SimpleTest.finish();
+      finish();
     };
 
     worker.onmessage = function(event) {
       is(event.data.size, expectedLength, "size property of slice is incorrect.");
       is(event.data.type, contentType ? contentType : blob.type, "type property of slice is incorrect.");
-      SimpleTest.finish();
+      finish();
     };
 
     var params = {blob: blob, start: start, end: end, contentType: contentType};
     worker.postMessage(params);
-    SimpleTest.waitForExplicitFinish();
+    waitForWorkerFinish();
   }
 
   // Empty file.
diff --git a/dom/workers/test/test_filePosting.xul b/dom/workers/test/test_filePosting.xul
index a84879d8dea..331f84b4908 100644
--- a/dom/workers/test/test_filePosting.xul
+++ b/dom/workers/test/test_filePosting.xul
@@ -6,10 +6,9 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=664783
 -->
 <window title="Mozilla Bug 664783"
         xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
-  <script type="application/javascript"
-          src="chrome://mochikit/content/MochiKit/packed.js"/>
   <script type="application/javascript"
           src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"/>
+  <script type="application/javascript" src="dom_worker_helper.js"/>
 
   <!-- test results are displayed in the html:body -->
   <body xmlns="http://www.w3.org/1999/xhtml">
@@ -62,7 +61,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=664783
 
     worker.onerror = function(event) {
       ok(false, "Worker had an error: " + event.data);
-      SimpleTest.finish();
+      finish();
     };
 
     worker.onmessage = function(event) {
@@ -70,11 +69,11 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=664783
       is(event.data.type, file.type, "type of file posted from worker does not match file posted to worker.");
       is(event.data.name, file.name, "name of file posted from worker does not match file posted to worker.");
       is(event.data.mozFullPath, file.mozFullPath, "mozFullPath of file posted from worker does not match file posted to worker.");
-      SimpleTest.finish();
+      finish();
     };
 
     worker.postMessage(file);
-    SimpleTest.waitForExplicitFinish();
+    waitForWorkerFinish();
   }
 
   // Empty file.
diff --git a/dom/workers/test/test_fileReadMozSlice.xul b/dom/workers/test/test_fileReadMozSlice.xul
index 88dcf1cf41e..c701585179f 100644
--- a/dom/workers/test/test_fileReadMozSlice.xul
+++ b/dom/workers/test/test_fileReadMozSlice.xul
@@ -6,10 +6,9 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=664783
 -->
 <window title="Mozilla Bug 664783"
         xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
-  <script type="application/javascript"
-          src="chrome://mochikit/content/MochiKit/packed.js"/>
   <script type="application/javascript"
           src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"/>
+  <script type="application/javascript" src="dom_worker_helper.js"/>
 
   <!-- test results are displayed in the html:body -->
   <body xmlns="http://www.w3.org/1999/xhtml">
@@ -61,17 +60,17 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=664783
 
     worker.onerror = function(event) {
       ok(false, "Worker had an error: " + event.data);
-      SimpleTest.finish();
+      finish();
     };
 
     worker.onmessage = function(event) {
       is(event.data, expectedText, "Text from sliced blob in worker is incorrect.");
-      SimpleTest.finish();
+      finish();
     };
 
     var params = {blob: blob, start: start, end: end};
     worker.postMessage(params);
-    SimpleTest.waitForExplicitFinish();
+    waitForWorkerFinish();
   }
 
   // Empty file.
diff --git a/dom/workers/test/test_fileReaderSync.xul b/dom/workers/test/test_fileReaderSync.xul
index f8735cf8b82..37033afbe47 100644
--- a/dom/workers/test/test_fileReaderSync.xul
+++ b/dom/workers/test/test_fileReaderSync.xul
@@ -6,10 +6,9 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=664783
 -->
 <window title="Mozilla Bug 664783"
         xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
-  <script type="application/javascript"
-          src="chrome://mochikit/content/MochiKit/packed.js"/>
   <script type="application/javascript"
           src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"/>
+  <script type="application/javascript" src="dom_worker_helper.js"/>
 
   <!-- test results are displayed in the html:body -->
   <body xmlns="http://www.w3.org/1999/xhtml">
@@ -82,19 +81,19 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=664783
       is(event.data.bin, fileData, "readAsBinaryString in worker returned incorrect result.");
       is(event.data.url, convertToDataURL("application/octet-stream", fileData), "readAsDataURL in worker returned incorrect result.");
       is(event.data.arrayBuffer.byteLength, fileData.length, "readAsArrayBuffer returned buffer of incorrect length.");
-      SimpleTest.finish();
+      finish();
     };
 
     worker.onerror = function(event) {
       ok(false, "Worker had an error: " + event.data);
-      SimpleTest.finish();
+      finish();
     };
 
     var params = {file: createFileWithData(fileData), encoding: encoding};
 
     worker.postMessage(params);
 
-    SimpleTest.waitForExplicitFinish();
+    waitForWorkerFinish();
   }
 
   /**
@@ -105,20 +104,20 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=664783
 
     worker.onerror = function(event) {
       ok(false, "Worker had an error: " + event.data);
-      SimpleTest.finish();
+      finish();
     };
 
     var k = 0;
     worker.onmessage = function(event) {
       is(event.data.url, expected[k], "readAsDataURL in worker returned incorrect result when reusing FileReaderSync.");
       k++;
-      SimpleTest.finish();
+      finish();
     };
 
     for (var i = 0; i < files.length; ++i) {
       var params = {file: files[i], encoding: undefined};
       worker.postMessage(params);
-      SimpleTest.waitForExplicitFinish();
+      waitForWorkerFinish();
     }
   }
 
@@ -130,19 +129,19 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=664783
 
     worker.onerror = function(event) {
       ok(false, "Worker had an error: " + event.data);
-      SimpleTest.finish();
+      finish();
     };
 
     var k = 0;
     worker.onmessage = function(event) {
       is(event.data.text, expected[k++], "readAsText in worker returned incorrect result when reusing FileReaderSync.");
-      SimpleTest.finish();
+      finish();
     };
 
     for (var i = 0; i < fileData.length; ++i) {
       var params = {file: createFileWithData(fileData[i]), encoding: undefined};
       worker.postMessage(params);
-      SimpleTest.waitForExplicitFinish();
+      waitForWorkerFinish();
     }
   }
 
@@ -158,19 +157,19 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=664783
       var view = new Uint8Array(event.data.arrayBuffer);
       is(event.data.arrayBuffer.byteLength, fileData.length, "readAsArrayBuffer returned buffer of incorrect length.");
       is(String.fromCharCode.apply(String, view), fileData, "readAsArrayBuffer returned buffer containing incorrect data.");
-      SimpleTest.finish();
+      finish();
     };
 
     worker.onerror = function(event) {
       ok(false, "Worker had an error: " + event.data);
-      SimpleTest.finish();
+      finish();
     };
 
     var params = {file: createFileWithData(fileData), encoding: undefined};
 
     worker.postMessage(params);
 
-    SimpleTest.waitForExplicitFinish();
+    waitForWorkerFinish();
   }
 
   // Empty file.
diff --git a/dom/workers/test/test_fileReaderSyncErrors.xul b/dom/workers/test/test_fileReaderSyncErrors.xul
index 6e7e630be59..2c3fa1ece1d 100644
--- a/dom/workers/test/test_fileReaderSyncErrors.xul
+++ b/dom/workers/test/test_fileReaderSyncErrors.xul
@@ -6,10 +6,9 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=664783
 -->
 <window title="Mozilla Bug 664783"
         xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
-  <script type="application/javascript"
-          src="chrome://mochikit/content/MochiKit/packed.js"/>
   <script type="application/javascript"
           src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"/>
+  <script type="application/javascript" src="dom_worker_helper.js"/>
 
   <!-- test results are displayed in the html:body -->
   <body xmlns="http://www.w3.org/1999/xhtml">
@@ -60,13 +59,13 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=664783
 
     worker.onerror = function(event) {
       ok(false, "Worker had an error: " + event.data);
-      SimpleTest.finish();
+      finish();
     };
 
     worker.onmessage = function(event) {
       if(event.data == undefined) {
         // Worker returns undefined when tests have finished running.
-        SimpleTest.finish();
+        finish();
       } else {
         // Otherwise worker will return results of tests to be evaluated.
         is(event.data.actual, event.data.expected, event.data.message);
@@ -74,7 +73,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=664783
     };
 
     worker.postMessage(file);
-    SimpleTest.waitForExplicitFinish();
+    waitForWorkerFinish();
   }
 
   // Run worker which creates exceptions.
diff --git a/dom/workers/test/test_fileSubWorker.xul b/dom/workers/test/test_fileSubWorker.xul
index b61716cf866..69f1d101240 100644
--- a/dom/workers/test/test_fileSubWorker.xul
+++ b/dom/workers/test/test_fileSubWorker.xul
@@ -6,10 +6,9 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=664783
 -->
 <window title="Mozilla Bug 664783"
         xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
-  <script type="application/javascript"
-          src="chrome://mochikit/content/MochiKit/packed.js"/>
   <script type="application/javascript"
           src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"/>
+  <script type="application/javascript" src="dom_worker_helper.js"/>
 
   <!-- test results are displayed in the html:body -->
   <body xmlns="http://www.w3.org/1999/xhtml">
@@ -61,7 +60,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=664783
 
     worker.onerror = function(event) {
       ok(false, "Worker had an error: " + event.data);
-      SimpleTest.finish();
+      finish();
     };
 
     worker.onmessage = function(event) {
@@ -73,11 +72,11 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=664783
         is(event.data.name, file.name, "name proproperty accessed from worker is incorrect.");
         is(event.data.mozFullPath, file.mozFullPath, "mozFullPath proproperty accessed from worker is not the same as on main thread.");
       }
-      SimpleTest.finish();
+      finish();
     };
 
     worker.postMessage(file);
-    SimpleTest.waitForExplicitFinish();
+    waitForWorkerFinish();
   }
 
   // Empty file.
diff --git a/dom/workers/test/test_workersDisabled.xul b/dom/workers/test/test_workersDisabled.xul
index fd6bf79c82d..1674f819fe6 100644
--- a/dom/workers/test/test_workersDisabled.xul
+++ b/dom/workers/test/test_workersDisabled.xul
@@ -8,6 +8,7 @@
         onload="test();">
   <script type="application/javascript"
           src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"/>
+  <script type="application/javascript" src="dom_worker_helper.js"/>
 
   <script type="application/javascript">
   <![CDATA[
@@ -30,11 +31,11 @@
       worker.onmessage = function(event) {
         is(event.data, message, "Good message.");
         prefs.clearUserPref(enabledPref);
-        SimpleTest.finish();
+        finish();
       }
       worker.postMessage(message);
 
-      SimpleTest.waitForExplicitFinish();
+      waitForWorkerFinish();
     }
   ]]>
   </script>
