LayoutTests/media/video-src-set.html

<video controls></video>
<div>Test that setting src attribute triggers load</div>
<script src=media-file.js></script>
<script src=video-test.js></script>
<script>
    var mediaFile = findMediaFile("video", "content/test");
    video.setAttribute('src', mediaFile);

    waitForEvent('loadstart', function () {
        testExpected("stripExtension(relativeURL(video.currentSrc))", stripExtension(mediaFile));
        endTest();
    } );

    video.setAttribute('src', mediaFile);
</script>