message: invokes a callback online a specific time
diff: @@ -59,5 +59,16 @@ define(["Tone/core/Tone", "deps/chai", "Tone/core/Context"], function (Tone, cha
  }
  };
  + //invoked only once
  + Test.atTime = function(when, callback){
  + var wasInvoked = false;
  + return function(time){
  + if (time >= when && !wasInvoked){
  + callback(time);
  + wasInvoked = true;
  + }
  + };
  + };
  +
  return Test;
  });
  \ No newline at end of file
  