Python Testing with pytest

Testing with Typer

A great feature of Typer is that it provides a testing interface. With it, we can call our application without having to resort to using subprocess.run, which is good, because we can’t mock stuff running in a separate process. (We looked at a short example of using subprocess.run with test_version_v1 in ​Using capsys​.) We just need to give the runner’s invoke function our app—cards.app—and a list of strings that represents the command.

Here’s an example of invoking the version function:

ch10/test_typer_testing.py

from typer.testing import CliRunner
from cards.cli import app

runner = CliRunner()


def test_typer_runner():
    result = runner.invoke(app, ["version"])
    print()
    print(f"version: ...