code: func (c *Cmd) Expect(response interface{}) *Cmd {
  	c.Responses = append(c.Responses, Response{response, nil})
  	return c
  }
docs: // Expect sets a response for this command. Every time a Do or Receive method
  // is executed for a registered command this response or error will be
  // returned. Expect call returns a pointer to Cmd struct, so you can chain
  // Expect calls. Chained responses will be returned on subsequent calls
  // matching this commands arguments in FIFO order