How to write an App

Writing a console application in python is quite easy. Basically, every script is a kind of application. The tricky part is to test it, therefore we suggest the following structure to achieve almost 100% coverage.

Application

You should implement the following functions in your application-script. The script should be placed in src/pixie/apps.

1. Necessary imports:

   import argparse
   import sys
   

2. Define ArgumentParser:

   def get_parser():
       parser = argparse.ArgumentParser()
       parser.add_argument(...)
       return parser
   

3. Parse commandline argument to dict:

   def parse_command_line_args(args=None):
       parsed_args = get_parser().parse_args(args)
       return vars(parsed_args)
   

4. Implement main-function:

   def main(**kwargs):
       # Implement your app
       return exitcode
   

5. Add entrypoint to script:

   if __name__ == "__main__":
       sys.exit(main(**parse_command_line_args()))
   

Test

import shlex
import pixie.apps.application


def test___application___golden_run___no_error_raised():
    command_line = \
        " ".join(positional_arguments) + \
        f" -a {argument_a}" \
        f" -b {argument_b}"

    command_line_args = pixie.apps.application.parse_command_line_args(shlex.split(
        command_line,
        posix=os.name == "posix"
    ))
    exitcode = pixie.apps.application.main(**command_line_args)

    assert exitcode == 0