code: func (mock *Mock) When(methodName string) *WhenResp {
  	resp := &WhenResp{
  		methodName: methodName,
  	}
  	mock.responses = append(mock.responses, resp)
  	return resp
  }
docs: // When defines name of the related method. It creates a new instance of WhenResp with provided method name and
  // stores it to the mock.