diff --git a/dom/base/test/file_timer_flood.html b/dom/base/test/file_timer_flood.html
index dc729d7e4214..94647d1750bf 100644
--- a/dom/base/test/file_timer_flood.html
+++ b/dom/base/test/file_timer_flood.html
@@ -3,15 +3,25 @@
 <body>
 <script>
 let count = 0;
-function cb() {
+let last_timer_set = 0;
+let last_timer_observed = 0;
+function cb(timer_observed) {
+  if (timer_observed > last_timer_observed) {
+    // In order to make the test more efficient, we don't use the SimpleTest
+    // ok() function to avoid generating one test assertion per one of these
+    // checks.  We only send a message to the parent which fails the test if
+    // we detect out of order firing of timeouts.
+    window.parent.postMessage('OUT_OF_ORDER', '*');
+  }
+  last_timer_observed = timer_observed;
   count += 1;
   // Notify our parent that we are ready once the timer flood has
   // warmed up.
   if (count === 10000) {
     window.parent.postMessage('STARTED', '*');
   }
-  setTimeout(cb, 0);
-  setTimeout(cb, 0);
+  last_timer_set = setTimeout(cb.bind(last_timer_set), 0);
+  last_timer_set = setTimeout(cb.bind(last_timer_set), 0);
 }
 addEventListener('load', cb);
 </script>
diff --git a/dom/base/test/test_timer_flood.html b/dom/base/test/test_timer_flood.html
index b74b04cf2983..8dfe59316067 100644
--- a/dom/base/test/test_timer_flood.html
+++ b/dom/base/test/test_timer_flood.html
@@ -20,15 +20,24 @@ function onLoad() {
   });
 }
 
+function setPrefs() {
+  // Put timeouts randomly in the tracking or normal buffer.  We do this in order to
+  // test to ensure that by default, this will not change the scheduling of timeouts.
+  return SpecialPowers.pushPrefEnv({"set": [["dom.timeout_bucketing_strategy", 3]]});
+}
+
 // Create a frame that executes a timer flood.  The frame signals
 // that is ready once the flood has had a chance to warm up.
 function withFloodFrame() {
-  return new Promise(resolve => {
+  return new Promise((resolve, reject) => {
     let frame = document.createElement('iframe');
     addEventListener('message', function onMsg(evt) {
       if (evt.data === 'STARTED') {
         removeEventListener('message', onMsg);
         resolve(frame);
+      } else if (evt.data == 'OUT_OF_ORDER') {
+        ok(false, "Out of order timeout observed");
+        reject();
       }
     });
     frame.src = 'file_timer_flood.html';
@@ -75,7 +84,9 @@ function testRequestAnimationFrame() {
 
 let floodFrame;
 
-onLoad().then(_ => {
+onLoad()
+.then(setPrefs)
+.then(_ => {
   // Start a timer flood in a frame.
   return withFloodFrame();
 }).then(frame => {
@@ -109,6 +120,8 @@ onLoad().then(_ => {
   ok(true, 'completed tests without timing out');
   floodFrame.remove();
   SimpleTest.finish();
+}).catch(_ => {
+  SimpleTest.finish();
 });
 </script>
 </pre>
