写了一个简单 Python 测试脚本，请问一下为什么运行显示测试用例为 0，我这里已经定义一个了吧

import unittest                                                                                     
                                                                                                     
from viman import vimanApp                                                                          
                                                                                                     
class cli_tests(unittest.TestCase):                                                                 
    argv_set = [                                                                                    
            ['viman', '-h'],                                                                        
            ['viman', '-V'],                                                                        
            ['viman', '-Q'],                                                                        
            ['viman', '-Sf', 'test.yml'],                                                           
            ['viman', '-S', 'https://github.com/vimscript/vim-snippets.git'],   
            ['viman', '-Ur'],                                                                       
            ['viman', '-R', 'https://github.com/vimscript/vim-snippets.git'],   
            ['viman', '-Rn', 'a.vim'],                                                              
            ['viman', '-Rf', '~/.viman.yml'],                                                       
        ]                                                                                           
                                                                                                    
    def cli_testing(self):                                                                          
        for argv in cli_tests.argv_set:                                                             
            self.assertEqual(vimanApp.main(argv), 0)                                                
                                                                                                    
                                                                                                    
if __name__ == '__main__':                                                                          
    unittest.main()