Tone.js/test/helper/PassAudio.js

import Test from "helper/Test";
import Offline from "Tone/core/Offline";
import Signal from "Tone/signal/Signal";
import Master from "Tone/core/Master";

var PassAudio = 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 array = buffer.toMono().toArray();
		for (var i = 0; i < array.length; i++){
			var time = (i / array.length) * duration;
			var sample = array[i];
			if (time >= duration / 2 && sample !== 0){
				return true;
			} else if (time < duration / 2){
				expect(sample).to.be.closeTo(0, 0.001);
			}
		}
		throw new Error("node outputs silence");
	});
};

export default PassAudio;