How to do unit test for input argument from command line?

Question

I have a python script supporting some commands with arguments. I need to add the unit test for the commands with arguments.

I have the code below which works fine.

#!/usr/bin/python3.7
#
import argparse
import sys
import re
def isStringValid(string):
 regex = re.compile('[@_!#$%^&*()<>?/\|}{~:]')
 if regex.search(string) is None:
 return True
 else:
 return False
class App(object):
 def __init__(self):
 parser = argparse.ArgumentParser(
 description='App script',
 usage='''./app.py <command> [<args>]
The most commonly used ts commands are:
 width Get width
 play <file> Play audio file
''')
 parser.add_argument('command', help='Subcommand to run')
 args = parser.parse_args(sys.argv[1:2])
 if not hasattr(self, args.command):
 print('Unrecognized command')
 parser.print_help()
 exit(1)
 getattr(self, args.command)()
 @staticmethod
 def width():
 parser = argparse.ArgumentParser(
 description='Get width')
 args = parser.parse_args(sys.argv[2:])
 print('width: 10cm')
 @staticmethod
 def play():
 parser = argparse.ArgumentParser(
 description='Play audio file')
 parser.add_argument('value', help='Play audio file')
 args = parser.parse_args(sys.argv[2:])
 if args.value is not None:
 result = isStringValid(args.value)
 if result is True:
 # Play audio file
 print('play: OK')
 else:
 print('play: invalid input! Error Code: 1')
if __name__ == '__main__':
 App()

Here is the unit test. I implemented the unit test for 'width' command. But for 'play' command. I don't know how to add unit test for it. Basically, I need to test the input argument "play ring.wav" which is valid input. I also need to test the input argument "play ring^&.wav" which is invalid. But how to add unit test for these test cases?

#!/usr/bin/python3.7
import unittest
import argparse
from app import *
class TestApp(unittest.TestCase):
 def test_width(self):
 result = App.width()
 self.assertEqual(result, None)
 #def test_play_valid(self):
 # need to test the input argument "play ring.wav", but how?
 #def test_play_invalid(self):
 # need to test the input argument "play ring^&.wav", but how?
if __name__ == '__main__':
 unittest.main()

What I need is: have unit test do the testing instead of doing this by typing the command manually:

$ ./app.py play ring.wav
play: OK
$ ./app.py play ring~%.wav
play: invalid input! Error Code: 1

• JeffUK: Possible duplicate of How to unittest command line arguments?
• Blorgbeard: You're not really testing anything meaningful for width, since it just prints and returns None. So does play, though, so if you consider your test_width good, then just do exactly the same for play.
• Konrad Rudolph: if ...: return True else: return False is an anti-pattern. Instead, do return ... directly.