diff --git a/content/media/webaudio/test/webaudio.js b/content/media/webaudio/test/webaudio.js
new file mode 100644
index 000000000000..4de8715b8b2f
--- /dev/null
+++ b/content/media/webaudio/test/webaudio.js
@@ -0,0 +1,14 @@
+// Helpers for Web Audio tests
+
+function expectException(func, exceptionCode) {
+  var threw = false;
+  try {
+    func();
+  } catch (ex) {
+    threw = true;
+    ok(ex instanceof DOMException, "Expect a DOM exception");
+    ok(ex.code, exceptionCode, "Expect the correct exception code");
+  }
+  ok(threw, "The exception was thrown");
+}
+