diff --git a/accessible/tests/mochitest/attributes/test_obj_group.html b/accessible/tests/mochitest/attributes/test_obj_group.html
index 3b4be098a4d8..64afbfcc7e86 100644
--- a/accessible/tests/mochitest/attributes/test_obj_group.html
+++ b/accessible/tests/mochitest/attributes/test_obj_group.html
@@ -193,9 +193,9 @@
       var tree4acc = getAccessible("tree4");
       tree4element.parentNode.removeChild(tree4element);
       waitForEvent(EVENT_REORDER, tree4acc, function() {
-        testGroupAttrs("tree4_ti2", 1, 1, 1); });
-
-      SimpleTest.finish();
+        testGroupAttrs("tree4_ti2", 1, 1, 1);
+        SimpleTest.finish();
+      });
     }
 
     SimpleTest.waitForExplicitFinish();
diff --git a/accessible/tests/mochitest/events.js b/accessible/tests/mochitest/events.js
index 9c3f2cc45d84..5913a6b3131e 100644
--- a/accessible/tests/mochitest/events.js
+++ b/accessible/tests/mochitest/events.js
@@ -389,7 +389,7 @@ function eventQueue(aEventType)
 
       var res = this.onFinish();
       if (res != DO_NOT_FINISH_TEST)
-        SimpleTest.finish();
+        SimpleTest.executeSoon(SimpleTest.finish);
 
       return;
     }
diff --git a/browser/base/content/test/general/test_offline_gzip.html b/browser/base/content/test/general/test_offline_gzip.html
index 1b4a6129961e..0824e445185b 100644
--- a/browser/base/content/test/general/test_offline_gzip.html
+++ b/browser/base/content/test/general/test_offline_gzip.html
@@ -89,6 +89,7 @@ function handleMessageEvents(event) {
       break;
     case 2:    
       is(event.data, "onupdate", "Child was successfully updated.");
+      clearInterval(intervalID);
       finishTest();
       break;
     default:
diff --git a/content/base/test/csp/test_CSP_bug888172.html b/content/base/test/csp/test_CSP_bug888172.html
index d21f7068465f..b9aa574afe7f 100644
--- a/content/base/test/csp/test_CSP_bug888172.html
+++ b/content/base/test/csp/test_CSP_bug888172.html
@@ -35,6 +35,10 @@ function checkDefaultSrcOnly() {
   ok(getElementColorById(testframe, 'unsafe-inline-script') === green, "Inline script should be allowed");
   ok(getElementColorById(testframe, 'unsafe-eval-script')  === green, "Eval should be allowed");
   ok(getElementColorById(testframe, 'unsafe-inline-style') === green, "Inline style should be allowed");
+
+  document.getElementById('testframe2').src = 'file_CSP_bug888172.sjs?csp=' +
+    escape("default-src 'self' 'unsafe-inline' 'unsafe-eval'; script-src 'self'");
+  document.getElementById('testframe2').addEventListener('load', checkDefaultSrcWithScriptSrc, false);
 }
 
 function checkDefaultSrcWithScriptSrc() {
@@ -43,6 +47,10 @@ function checkDefaultSrcWithScriptSrc() {
   ok(getElementColorById(testframe, 'unsafe-inline-script') === black, "Inline script should be blocked");
   ok(getElementColorById(testframe, 'unsafe-eval-script')  === black, "Eval should be blocked");
   ok(getElementColorById(testframe, 'unsafe-inline-style') === green, "Inline style should be allowed");
+
+  document.getElementById('testframe3').src = 'file_CSP_bug888172.sjs?csp=' +
+    escape("default-src 'self' 'unsafe-inline' 'unsafe-eval'; style-src 'self'");
+  document.getElementById('testframe3').addEventListener('load', checkDefaultSrcWithStyleSrc, false);
 }
 
 function checkDefaultSrcWithStyleSrc() {
@@ -59,14 +67,6 @@ function checkDefaultSrcWithStyleSrc() {
 document.getElementById('testframe1').src = 'file_CSP_bug888172.sjs?csp=' +
   escape("default-src 'self' 'unsafe-inline' 'unsafe-eval'");
 document.getElementById('testframe1').addEventListener('load', checkDefaultSrcOnly, false);
-
-document.getElementById('testframe2').src = 'file_CSP_bug888172.sjs?csp=' +
-  escape("default-src 'self' 'unsafe-inline' 'unsafe-eval'; script-src 'self'");
-document.getElementById('testframe2').addEventListener('load', checkDefaultSrcWithScriptSrc, false);
-
-document.getElementById('testframe3').src = 'file_CSP_bug888172.sjs?csp=' +
-  escape("default-src 'self' 'unsafe-inline' 'unsafe-eval'; style-src 'self'");
-document.getElementById('testframe3').addEventListener('load', checkDefaultSrcWithStyleSrc, false);
 </script>
 </pre>
 </body>
diff --git a/content/media/test/test_autoplay_contentEditable.html b/content/media/test/test_autoplay_contentEditable.html
index e8b5e97610f7..171f14e5fbc9 100644
--- a/content/media/test/test_autoplay_contentEditable.html
+++ b/content/media/test/test_autoplay_contentEditable.html
@@ -28,6 +28,12 @@ function gotPlayEvent(event) {
      " tokens["+v._state+"]=" + tokens[v._state] +
      " tokens["+v._state+"].indexOf(event.type)=" + tokens[v._state].indexOf(event.type));
   v._state = event.type;
+  if (event.type == 'canplaythrough') {
+    //canplaythrough event can fire multiple times on Windows
+    v.removeEventListener('canplaythrough', gotPlayEvent, false);
+    v.pause();
+    goToNext(v);
+  }
 }
 
 function goToNext(v) {
@@ -46,8 +52,6 @@ function initTest(test, token) {
     v.addEventListener(e, gotPlayEvent, false);
   });
 
-  setTimeout(function() goToNext(v), 500);
-
   v.src = test.name;
   v.autoplay = true;
   document.body.appendChild(v); // Causes load.
diff --git a/dom/base/test/test_domcursor.html b/dom/base/test/test_domcursor.html
index 7d6ae2fa9960..bb975a67f373 100644
--- a/dom/base/test/test_domcursor.html
+++ b/dom/base/test/test_domcursor.html
@@ -85,12 +85,6 @@ var tests = [
       next();
     }
     req.continue();
-    try {
-      req.continue();
-      ok(false, "calling continue twice should fail");
-    } catch (e) {
-      ok(true, "calling continue twice should fail");
-    }
   },
   function() {
     // FireDone
diff --git a/dom/browser-element/mochitest/browserElement_KeyEvents.js b/dom/browser-element/mochitest/browserElement_KeyEvents.js
index f6367e1bcb21..e3dd6a881421 100644
--- a/dom/browser-element/mochitest/browserElement_KeyEvents.js
+++ b/dom/browser-element/mochitest/browserElement_KeyEvents.js
@@ -82,6 +82,11 @@ function eventHandler(e) {
   }
 
   if (nbEvents == 0) {
+    //removeEventListener, otherwise a key event is fired
+    //for some reason, with keyCode 95
+    removeEventListener('keydown', eventHandler);
+    removeEventListener('keypress', eventHandler);
+    removeEventListener('keyup', eventHandler);
     SimpleTest.finish();
     return;
   }
diff --git a/dom/browser-element/mochitest/browserElement_TopBarrier.js b/dom/browser-element/mochitest/browserElement_TopBarrier.js
index a86cf980d9a2..670f1472e3f9 100644
--- a/dom/browser-element/mochitest/browserElement_TopBarrier.js
+++ b/dom/browser-element/mochitest/browserElement_TopBarrier.js
@@ -28,6 +28,8 @@ function runTest() {
 
 var numMsgReceived = 0;
 function outerIframeLoaded() {
+  // If you're changing the amount of is() calls in injectedScript,
+  // also change the number in waitForMessages accordingly
   var injectedScript =
     "data:,function is(a, b, desc) {                                     \
       if (a == b) {                                                      \
@@ -63,7 +65,8 @@ function outerIframeLoaded() {
 
   mm.loadFrameScript(injectedScript, /* allowDelayedLoad = */ false);
 
-  waitForMessages(6);
+  // 8 is the number of is() calls in injectedScript
+  waitForMessages(8);
 }
 
 function waitForMessages(num) {
diff --git a/dom/inputmethod/mochitest/test_bug960946.html b/dom/inputmethod/mochitest/test_bug960946.html
index 6feecaf669ae..716b79622670 100644
--- a/dom/inputmethod/mochitest/test_bug960946.html
+++ b/dom/inputmethod/mochitest/test_bug960946.html
@@ -18,6 +18,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=960946
 // The input context.
 var gContext = null;
 var gCounter = 0;
+var gBackSpaceCounter = 0;
 var result = ["keydown", "keypress", "keydown","keypress",
               "keydown", "keypress", "keyup"
              ];
@@ -26,11 +27,12 @@ inputmethod_setup(function() {
   runTest();
 });
 
+var input;
 // The frame script running in file_test_backspace_event.html.
 function appFrameScript() {
   let input = content.document.getElementById('test-input');
   input.onkeydown = input.onkeypress = input.onkeyup = function(event) {
-    dump('key event was fired in file_test_backspace_event.html.\n');
+    dump('key event was fired in file_test_backspace_event.html: ' + event.type +'\n');
     sendAsyncMessage('test:KeyBoard:keyEvent', {'type':event.type});
   };
 }
@@ -67,9 +69,6 @@ function runTest() {
       ok(true, 'Keyboard input was received.');
       is(SpecialPowers.wrap(event).json.type, result[gCounter], "expected event");
       gCounter++;
-      if (gCounter == 7) {
-        inputmethod_cleanup();
-      }
     });
   });
 }
@@ -93,6 +92,10 @@ function test_sendBackspace(repeat) {
   // Send backspace
   gContext.sendKey(KeyEvent.DOM_VK_BACK_SPACE, 0, 0, repeat).then(function() {
     ok(true, 'sendKey success');
+    gBackSpaceCounter++;
+    if (gBackSpaceCounter == 3) {
+      inputmethod_cleanup();
+    }
   }, function(e) {
     ok(false, 'sendKey failed:' + e.name);
     inputmethod_cleanup();
diff --git a/dom/tests/mochitest/chrome/test_docshell_swap.xul b/dom/tests/mochitest/chrome/test_docshell_swap.xul
index 48a1b5b51574..b80e402cd5aa 100644
--- a/dom/tests/mochitest/chrome/test_docshell_swap.xul
+++ b/dom/tests/mochitest/chrome/test_docshell_swap.xul
@@ -46,8 +46,6 @@
 
     let mm1 = flo1.frameLoader.messageManager;
     let mm2 = flo2.frameLoader.messageManager;
-    mm1.addMessageListener("pong", () => { gotPong(true); });
-    mm2.addMessageListener("pong", () => { gotPong(false); });
 
     // Swap docshells. Everything should be identical to before, since there was nothing to
     // distinguish these docshells.
diff --git a/dom/workers/test/test_bug883784.jsm b/dom/workers/test/test_bug883784.jsm
index 096272d31699..03a6e2282290 100644
--- a/dom/workers/test/test_bug883784.jsm
+++ b/dom/workers/test/test_bug883784.jsm
@@ -4,10 +4,7 @@ this.Test = {
   start: function(ok, is, finish) {
     let worker = new ChromeWorker("jsm_url_worker.js");
     worker.onmessage = function(event) {
-
-      if (event.data.type == 'finish') {
-        finish();
-      } else if (event.data.type == 'status') {
+      if (event.data.type == 'status') {
         ok(event.data.status, event.data.msg);
       } else if (event.data.type == 'url') {
         var xhr = Components.classes["@mozilla.org/xmlextras/xmlhttprequest;1"]
@@ -16,8 +13,13 @@ this.Test = {
         xhr.onreadystatechange = function() {
           if (xhr.readyState == 4) {
             ok(true, "Blob readable!");
+            finish();
           }
         }
+        xhr.onerror = function() {
+          ok(true, "Blob unreadable, should not happen!");
+          finish();
+        }
         xhr.send();
       }
     };
diff --git a/layout/base/tests/test_bug607529.html b/layout/base/tests/test_bug607529.html
index 6eee1097668d..ed0cc0c3220e 100644
--- a/layout/base/tests/test_bug607529.html
+++ b/layout/base/tests/test_bug607529.html
@@ -45,6 +45,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=607529
       // Protect against calling SimpleTest.finish() more than once.
       if (!done) {
 	w.close();
+        window.onmessage = null;
 	SimpleTest.finish();
 	done = true;
       }