Python Testing with pytest

Mocking a Class and Methods

Let’s take a look at how to test config:

cards_proj/src/cards/cli.py

@app.command()
def config():
    """List the path to the Cards db."""
    with cards_db() as db:
        print(db.path())

The cards_db() is a context manager that returns a cards.CardsDB object. The returning object is then used as db to call db.path(). So we have two things to mock: cards.CardsDB and one of its methods, path().

We’ll start with the class:

ch10/test_mock.py

def test_mock_CardsDB():
    with mock.patch.object(cards, "CardsDB") as MockCardsDB:
        print()
        print(f"       class:{MockCardsDB}")
        print(f"return_value:{MockCardsDB.return_value}")
        with cards.cli.cards_db() as db:
            print(f"      object:{db}")

This is ...