pytest Quick Start Guide

capsys/capfd

The capsys fixture captures all text written to sys.stdout and sys.stderr and makes it available during testing.

Suppose we have a small command-line script and want to check the usage instructions are correct when the script is invoked without arguments:

from textwrap import dedentdef script_main(args):    if not args:        show_usage()        return 0    ...def show_usage():    print("Create/update webhooks.")    print(" Usage: hooks REPO URL")

During testing, we can access the captured output, using the capsys fixture. This fixture has a capsys.readouterr() method that returns a namedtuple (https://docs.python.org/3/library/collections.html#collections.namedtuple) with out and err attributes, containing the captured text from sys.stdout and sys.stderr ...