Python Testing with pytest

Using monkeypatch

During the previous discussion of capsys, we used this code to test the output of the Cards project:

ch4/test_version.py

import cards


def test_version_v2(capsys):
    cards.cli.version()
    output = capsys.readouterr().out.rstrip()
    assert output == cards.__version__

That made a decent example of how to use capsys, but it’s still not how I prefer to test the CLI. The Cards application uses a library called Typer^[16] that includes a runner feature that allows us to test more of our code, makes it look more like a command-line test, remains in process, and provides us with output hooks. It’s used like this:

ch4/test_version.py

from typer.testing import CliRunner


def test_version_v3():
 runner = ...