test_countdown.py

import pytest

from itertools import islice

from countdown import countdown


@pytest.fixture
def cd():
    return countdown()


def test_generator_values(cd):
    actual = list(islice(cd, 0, 100))
    expected = [100, 99, 98, 97, 96, 95, 94, 93, 92, 91,
                90, 89, 88, 87, 86, 85, 84, 83, 82, 81,
                80, 79, 78, 77, 76, 75, 74, 73, 72, 71,
                70, 69, 68, 67, 66, 65, 64, 63, 62, 61,
                60, 59, 58, 57, 56, 55, 54, 53, 52, 51,
                50, 49, 48, 47, 46, 45, 44, 43, 42, 41,
                40, 39, 38, 37, 36, 35, 34, 33, 32, 31,
                30, 29, 28, 27, 26, 25, 24, 23, 22, 21,
                20, 19, 18, 17, 16, 15, 14, 13, 12, 11,
                10, 9, 8, 7, 6, 5, 4, 3, 2, 1]
    assert actual == expected


def test_going_beyond_one_hundred(cd):
    with pytest.raises(StopIteration):
        for _ in range(101):
            next(cd)