--- a/dom/media/mediasource/test/test_MediaSource.html
+++ b/dom/media/mediasource/test/test_MediaSource.html
@@ -35,16 +35,19 @@ runWithMSE(function () {
   v.src = o;
   document.body.appendChild(v);
 
   var loadedmetadataCount = 0;
   var updatestartCount = 0;
   var updateendCount = 0;
   var updateCount = 0;
 
+  ok(MediaSource.isTypeSupported("video/webm; codecs=vp8"), "VP8 MSE is always supported");
+  ok(MediaSource.isTypeSupported("audio/webm", "Audio MSE is always supported"));
+
   ms.addEventListener("sourceopen", function () {
     ok(true, "Receive a sourceopen event");
     is(ms.readyState, "open", "MediaSource must be in open state after sourceopen");
     var sb = ms.addSourceBuffer("video/webm");
     ok(sb, "Create a SourceBuffer");
     is(ms.sourceBuffers.length, 1, "MediaSource.sourceBuffers is expected length");
     is(ms.sourceBuffers[0], sb, "SourceBuffer in list matches our SourceBuffer");
     is(ms.activeSourceBuffers.length, 0, "MediaSource.activeSourceBuffers is expected length");