cycle_test.py

import pytest
from itertools import cycle as itertools_cycle

from src.repeatable import cycle
from .helpers import (
    counter, repeatable_counter, check_same_result, assert_memory_under,
    assert_memory_exceeds
)


@pytest.mark.parametrize(
    'args',
    [
        pytest.param((range(4),), id='single iterable'),
        pytest.param(([],), id='empty iterable'),
        pytest.param((repeatable_counter(4),), id='repeatable iterable'),
        pytest.param((repeatable_counter(0),), id='empty repeatable iterable'),
        pytest.param(tuple(), id='no inputs'),
        
        # `itertools.cycle` can yield some results before memory overflow
        pytest.param(
            (repeatable_counter(),),
            id='infinite repeatable'
        ),
    ]
)
def test_same_result(args):
    # `cycle` produces values indefinitely, so we will just check that
    # the generators begin the same way
    check_same_result(cycle, itertools_cycle, *args, stop=100)


''' this package's `cycle` implementation '''

@assert_memory_under(1)  # memory usage should not exceed 1MiB
def test_low_memory_usage_with_infinite_repeatables():
    result = cycle(repeatable_counter())

    for _ in range(int(1e6)):
        next(result)


@assert_memory_under(1)  # memory usage should not exceed 1MiB
def test_low_memory_usage_with_large_repeatables():
    result = cycle(repeatable_counter(stop=1e6))

    for _ in range(int(1e6)):
        next(result)


@assert_memory_exceeds(1)  # expect memory usage to be high
def test_high_memory_usage_with_infinite_vanilla_iterables():
    result = cycle(counter())

    for _ in range(int(1e6)):
        next(result)


''' existing `itertools.cycle` '''

@assert_memory_exceeds(1)  # expect memory usage to be high
def test_high_memory_usage_with_infinite_repeatables():
    result = itertools_cycle(repeatable_counter())

    for _ in range(int(1e6)):
        next(result)


@assert_memory_exceeds(1)  # expect memory usage to be high
def test_high_memory_usage_with_large_repeatables():
    result = itertools_cycle(repeatable_counter(stop=1e6))

    for _ in range(int(1e6)):
        next(result)


@assert_memory_exceeds(1)  # expect memory usage to be high
def test_itertools_high_memory_usage_with_infinite_vanilla_iterables():
    result = itertools_cycle(counter())

    for _ in range(int(1e6)):
        next(result)