Pytest: Calling a program with command line parameters

README.md

Pytest: Calling a program with command line parameters

The solution is based on monkeypatch fixture.

In this example myprog reads number from the file myprog_input.txt adds 2 to it and stores result in myprog_output.txt

Environment:

uname -vosri
Linux 4.4.0-19041-Microsoft #1237-Microsoft Sat Sep 11 14:32:00 PST 2021 x86_64 GNU/Linux

lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 20.04.3 LTS
Release:        20.04
Codename:       focal

python3.11 --version
Python 3.11.7

LICENSE

https://opensource.org/licenses/MIT

Copyright 2021 Dmitry Messerman

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files 
(the "Software"),  to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, 
publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, 
subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, 
INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. 
IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, 
WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

myprog.py

#!/usr/bin/python3.11
import argparse
import hashlib

def main():
    parser = argparse.ArgumentParser(description='myprog')
    parser.add_argument('-i')
    parser.add_argument('-o')
    args = parser.parse_args()
    with open(args.i) as f:
        input_data=int(f.read())
    output_data=input_data+2
    f.close()
    with open(args.o,"w") as fo:
        fo.write(str(output_data) + '\n')
    fo.close()
    with open(args.o) as fot:
        bytes = fot.read().encode() # read entire file as bytes
    fot.close()
    readable_hash = hashlib.sha256(bytes).hexdigest();
    return readable_hash 


if __name__ == '__main__':
    print(main())

myprog_input.txt

3

myprog_output_expected.txt

5

output.log

myprog.py -i myprog_input.txt -o myprog_output.txt
f0b5c2c2211c8d67ed15e75e656c7862d086e9245420892a7de62cd9ec582a06

runme

#!/usr/bin/tcsh -f
set script_realpath=`realpath $0`
set script_path=$script_realpath:h
\rm -f myprog_output.txt >& /dev/null
set hash_cmd="${script_path}/myprog.py -i ${script_path}/myprog_input.txt -o myprog_output.txt"
if(1 == `uname | grep ^MINGW | wc -l`) then
    set hash_val=`python3.10 $hash_cmd`
    unix2dos myprog_output.txt
else
    set hash_val=`$hash_cmd`
endif
diff myprog_output.txt ${script_path}/myprog_output_expected.txt
grep -w $hash_val ${script_path}/test_myprog.py
pytest ${script_path}/test_myprog.py

test.log

        assert myprog.main() == 'f0b5c2c2211c8d67ed15e75e656c7862d086e9245420892a7de62cd9ec582a06'
============================= test session starts ==============================
platform linux -- Python 3.11.1, pytest-7.2.0, pluggy-1.0.0
rootdir: /home/mdmitry/github/gist/pytest_program
collected 1 item

test_myprog.py .                                                         [100%]

============================== 1 passed in 0.04s ===============================

test_myprog.py

#!/usr/bin/python3.11
import sys
import myprog

def test_myprog(monkeypatch):
    with monkeypatch.context() as m:
        m.setattr(sys, 'argv', ['myprog', '-i', 'myprog_input.txt', '-o', 'myprog_output.txt'])
        assert myprog.main() == 'f0b5c2c2211c8d67ed15e75e656c7862d086e9245420892a7de62cd9ec582a06'