Tone.js/test/helper/PassAudioStereo.js

define(["Test", "Tone/core/Offline", "Tone/signal/Signal", "Tone/core/Master", "helper/BufferTest"], 
	function (Test, Offline, Signal, Master, BufferTest) {

	var PassAudioStereo = function(before){

		var duration = 0.2;
		return Offline(function(){
			var sig = new Signal(0);
			before(sig);
			sig.setValueAtTime(1, duration / 2);
		}, duration).then(function(buffer){
			var silent = true;
			BufferTest.forEach(buffer, function(l, r, time){
				if (time >= duration / 2 && l !== 0 && r !== 0){
					silent = false;
					return;
				} else if (time < duration / 2) {
					expect(l).to.be.closeTo(0, 0.001);
					expect(r).to.be.closeTo(0, 0.001);
				}
			});
			if (silent){
				throw new Error("node outputs silence");
			}
		});
	};

	return PassAudioStereo;
});