--- a/dom/media/test/test_seekToNextFrame.html
+++ b/dom/media/test/test_seekToNextFrame.html
@@ -27,17 +27,19 @@ function startTest(test, token) {
   manager.started(token, handler);
 
   v.src = test.name;
   v.name = test.name;
 
   function callSeekToNextFrame() {
     v.seekToNextFrame().then(
       () => {
-        ok(v.seenSeeking, "Should have already received seeking event.")
+        if (!v.seenSeeking) {
+          ok(false, v.token + ": Should have already received seeking event.");
+        }
         v.seenSeeking = false;
         if (!v.seenEnded)
           callSeekToNextFrame();
       },
       () => {
         // When seek reaches the end, the promise is resolved before 'ended'
         // is fired. The resolver calls callSeekToNextFrame() to schedule
         // another seek and then the 'ended' handler calls finish() to shut
@@ -61,17 +63,19 @@ function startTest(test, token) {
   }
 
   var onEnded = function(test, v) { return function() {
     v.seenEnded = true;
     finish();
   }}(test, v);
 
   var onSeeking = function(test, v) { return function() {
-    ok(!v.seenSeeking, "Should yet receive seeking event.")
+    if (v.seenSeeking) {
+      ok(false, v.token + ": Should yet receive seeking event.");
+    }
     v.seenSeeking = true;
   }}(test, v);
 
   v.addEventListener("loadedmetadata", onLoadedmetadata);
   v.addEventListener("seeking", onSeeking);
   v.addEventListener("ended", onEnded);
 
   document.body.appendChild(v);