Python Testing with pytest

Mocking an Attribute

Most of the Cards API is accessed through a CardsDB object, but one entry point is just an attribute, cards.__version__. Let’s look at how we can use mocking to make sure the value from cards.__version__ is correctly reported through the CLI.

There are several patch methods within the mock package. We’ll be using patch.object. We’ll use it primarily in its context manager form. Here’s what it looks like to mock __version__:

ch10/test_mock.py

from unittest import mock

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

runner = CliRunner()


def test_mock_version():
    with mock.patch.object(cards, "__version__", "1.2.3"):
 result = runner.invoke(app, ...