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... pytest.


Testing your code is a good idea because it usually leads to great improvements. There's many libraries in python that will help with testing but a favourable on called pytest. In this series of videos we demonstrate how the use it.


Notes

The files are now updated.

blackjack/common.py

def card_score(cards):
    if len(cards) < 2:
        raise ValueError("The `card_score` function requires at least 2 cards.")
    if not isinstance(cards, str):
        raise ValueError("The input for `card_score` needs to be a string.")
    numbers = [c for c in cards if c in "23456789"]
    faces = [c for c in cards if c in "JQK"]
    n_aces = sum([1 for c in cards if c == "A"])
    score = sum([int(i) for i in numbers]) + len(faces) * 10
    while n_aces > 0:
        score += 1 if score + 11 > 21 else 11
        n_aces -= 1
    return score if score <= 21 else 0

tests/test_blackjack.py

import pytest 

from blackjack.common import card_score

@pytest.mark.parametrize("cards,score", [('JK', 20), ('KKK', 0), ('AA', 12), ('AK', 21)])
def test_simple_usecase(cards, score):
    assert card_score(cards) == score

def test_raise_error():
    with pytest.raises(ValueError):
        card_score("")

There's still a hidden issue in our code though. We'll discuss it in a moment. Can you see it now allready?


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