--- a/dom/media/test/mochitest.ini
+++ b/dom/media/test/mochitest.ini
@@ -492,16 +492,17 @@ support-files =
   owl-funny-id3.mp3
   owl-funny-id3.mp3^headers^
   owl.mp3
   owl.mp3^headers^
   owl-short.mp3
   owl-short.mp3^headers^
   parser.vtt
   pixel_aspect_ratio.mp4
+  play_promise.js
   r11025_msadpcm_c1.wav
   r11025_msadpcm_c1.wav^headers^
   r11025_s16_c1.wav
   r11025_s16_c1.wav^headers^
   r11025_s16_c1_trailing.wav
   r11025_s16_c1_trailing.wav^headers^
   r11025_s16_c1-short.wav
   r11025_s16_c1-short.wav^headers^

new file mode 100644
--- /dev/null
+++ b/dom/media/test/play_promise.js
@@ -0,0 +1,3 @@
+function getNotSupportedFile(name) {
+  return name + ".bad";
+}
\ No newline at end of file