Black Jack Example

Black Jack Repo Project Example

• Sample Repo for this project

blackjack.py

def card_score(cards):
  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

test_blackjack.py

import pytest

from blackjack import card_score

def test_simple_usecase1():
  card_score("JK") == 20

def test_simple_usecase2():
  card_score("JKQ") == 0

def test_simple_usecase3():
  card_score("KA") == 21

def test_simple_usecase4():
  card_score("AA") == 12

• A more robust way to stay DRY is to use pytest (Private)

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

• Run tests with pytest --verbose or configure auto process to do that
  • pytest is looking for files and functions whose names begin with test_*
  • You can run singular unit tests with the following syntax:

pytest --verbose test_blackjack.py::test_Simple_case4

Blackjack with DRY Pytests

• pytest (Private) in a package

├── blackjack
│   ├── __init__.py
│   └── common.py
├── setup.py
└── tests
  ├── __init__.py
  └── test_blackjack.py

blackjack

• __init__.py should be empty
• common.py (user preference on naming, example said "common utilities")

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

• __init__.py should be empty
• 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

• To be able to work on the package in developer mode you'll need to run;
  • python setup.py develop
• And from here you can safely run pytest again.
• pytest --verbose
• pytest-cov for code coverage testing
  • python -m pip install pytest-cov
  • HTML output: pytest --cov blackjack --cov-report html
• Calm Code Conftest
  • For greater code reusability and provide data to the testing suite, you can use conftest.py in the tests directory
  • This allows you to repeat yourself less and have a single location that feeds data into the testing suite instead of making the data for each test individually.

from clumper import Clumper # our custom module
import pytest

@pytest.fixture(scope="module")
def base_clumper():
  data = [
	  {"data": [i for _ in range(2)], "i": i, "c": c}
	  for i, c in enumerate("abcdefghijklmnopqrstuvwxyz")
  ]
  return Clumper(data)

# So that tests like this:

def test_headtail_size():
  data = [{'i': i} for i in range(10)]
  c = Clumper(data)
  assert len(c.head(10)) == 10
  assert len(c.tail(10)) == 10
  assert len(c.head(5)) == 5
  assert len(c.tail(5)) == 5

# can become like:

def test_headtail_size(base_clumper):
  assert len(base_clumper.head(10)) == 10
  assert len(base_clumper.tail(10)) == 10
  assert len(base_clumper.head(5)) == 5
  assert len(base_clumper.tail(5)) == 5