我想调用方法“ download_and_save”，并验证在我的单元测试中正在调用“ grabFile”方法。我怎样才能做到这一点？

Question

导入异步 从ftplib导入FTP 导入回溯

FtpDownloader类：

def __init__(self, site_cofig, file_name):
    self.site_config = site_cofig
    self.file_name = file_name

def grabFile(self, host_name, user_name, password, guest_file_name, host_file_name):

    ftp = FTP(host_name)
    ftp.login(user_name, password)
    localfile = open(host_file_name, 'wb')
    ftp.retrbinary('RETR ' + guest_file_name, localfile.write, 1024)
    ftp.quit()
    localfile.close()

@asyncio.coroutine
def download_and_save(self):
    try:
        self.grabFile(self.site_config.host_name, self.site_config.user_name,
                      self.site_config.password, self.file_name,
                      self.file_name)

    except Exception as e:
        print(traceback.format_exc())

我想调用方法“ download_and_save”并确认在我的单元测试中正在调用“ grabFile”方法。我该怎么办？