pipe() from mute-stream is called each time Read runs, but the mute-stream is never closed, so if you call Read more than 11 times node throws an EventEmitter memory leak warning onto the console. I think adding a call to end() of mute-stream in done() would resolve the issue.
Adding a call to end() of mute-stream within the done function of read
End mute stream so it un-pipes
Fixed on f3fbf9a. (Had to do a few other things as well as end(), and also added a test.)