@Override
  public void start() throws InstantiationException {
    if (isFaulty) {
      throw new InstantiationException("This is a faulty MockNioServer");
    }
  }
Implementation of {@link NioServer} that can be used in tests.
<p/>
Does no network I/O for now and is useful only for start(), shutdown() tests.
ambry-api/src/test/java/com/github/ambry/rest/MockNioServer.java