feat: Add a dice rolling class
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gm_assistant/dice.py
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98
gm_assistant/dice.py
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# SPDX-FileCopyrightText: 2025 2025
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# SPDX-FileContributor: Gergely Polonkai
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#
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# SPDX-License-Identifier: GPL-3.0-or-later
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"""dice -- Utilities to deal with dice rolls"""
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import random
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import re
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DICE_DESCRIPTOR_PATTERN = re.compile(r"^([0-9]*d[0-9]+)([+-]([0-9]+|[0-9]*d[0-9]+))*$")
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class Die:
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"""A generic die rolling class"""
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def __init__(self, descriptor: str) -> None:
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self.positive_pool, self.negative_pool, self.modifier = self.parse(descriptor)
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@staticmethod
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def parse(descriptor: str) -> tuple[list[int], list[int], int]:
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"""Parse dice descriptors such as ``d6`` or ``3d8+2``
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:param descriptor: the dice descriptor
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:returns: a tuple with the number and types of posititve dice, the number and types of negative dice, and the
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constant modifier
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"""
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normalized_descriptor = "".join(c for c in descriptor if c != " ")
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if not normalized_descriptor:
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raise ValueError("Empty string cannot be parsed")
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if not DICE_DESCRIPTOR_PATTERN.match(normalized_descriptor):
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raise ValueError(f"Invalid dice descriptor {descriptor}")
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sign = "+"
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positive_pool = []
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negative_pool = []
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modifier = 0
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while normalized_descriptor:
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if (new_sign := normalized_descriptor[0]) in ("+", "-"):
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sign = new_sign
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normalized_descriptor = normalized_descriptor[1:]
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continue
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match = re.search(r"^([0-9]*)(d?)([0-9]+)", normalized_descriptor)
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# This will always pass as we already checked the descriptor against DICE_DESCRIPTOR_PATTERN; we need this
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# assertion to prevent mypy warnings
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assert match
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multiplier, has_d, die_max = match.groups()
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normalized_descriptor = normalized_descriptor[match.end() :]
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if has_d:
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count = int(multiplier) if multiplier else 1
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dice = [int(die_max) for _ in range(count)]
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if sign == "+":
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positive_pool.extend(dice)
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elif sign == "-": # pragma: no branch
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negative_pool.extend(dice)
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else:
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value = int(die_max)
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if sign == "-":
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value = 0 - value
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modifier += value
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return positive_pool, negative_pool, modifier
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@property
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def minimum(self) -> int:
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"""The lowest number this dice roller can yield"""
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return len(self.positive_pool) - sum(self.negative_pool) + self.modifier
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@property
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def maximum(self) -> int:
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"""The highest number this dice roller can yield"""
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return sum(self.positive_pool) - len(self.negative_pool) + self.modifier
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def roll(self) -> int:
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"""Roll the dice in this roller’s dice pool and return the result"""
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result = 0
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for die in self.positive_pool:
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result += random.randint(1, die)
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for die in self.negative_pool:
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result -= random.randint(1, die)
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result += self.modifier
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return result
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145
tests/test_dice.py
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tests/test_dice.py
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# SPDX-FileCopyrightText: 2025 2025
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# SPDX-FileContributor: Gergely Polonkai
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#
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# SPDX-License-Identifier: GPL-3.0-or-later
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"""Tests for the dice roller"""
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import pytest
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from pytest_mock import MockerFixture
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from gm_assistant.dice import Die
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def test_parse_empty() -> None:
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"""Test parsing an empty string"""
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with pytest.raises(ValueError):
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Die.parse("")
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with pytest.raises(ValueError):
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Die.parse(" ")
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@pytest.mark.parametrize("descriptor", [pytest.param("12", id="nodie")])
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def test_invalid(descriptor: str) -> None:
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"""Test parsing invalid descriptors"""
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with pytest.raises(ValueError):
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Die.parse(descriptor)
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@pytest.mark.parametrize(
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"descriptor,expected",
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[
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pytest.param("d6", ([6], [], 0), id="single"),
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pytest.param("2d6", ([6, 6], [], 0), id="multiple"),
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pytest.param("d12 + 1", ([12], [], 1), id="modifiedsingle"),
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pytest.param("3d12 - 2", ([12, 12, 12], [], -2), id="modifiedmultiple"),
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pytest.param("2d6+3d8-d4+1", ([6, 6, 8, 8, 8], [4], 1), id="complex"),
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],
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)
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def test_valid(descriptor: str, expected: tuple[list[int], list[int], int]) -> None:
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"""Test parsing valid descriptors"""
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results = Die.parse(descriptor)
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assert results == expected
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@pytest.mark.parametrize(
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"descriptor,expected",
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[
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pytest.param("d6", 1, id="single"),
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pytest.param("2d6", 2, id="multiple"),
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pytest.param("d12 + 1", 2, id="modifiedsingle"),
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pytest.param("3d12 - 2", 1, id="modifiedmultiple"),
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pytest.param("2d6+3d8-d4+1", 2, id="complex"),
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],
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)
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def test_minimum(descriptor: str, expected: int) -> None:
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"""Test the ``minimum`` property"""
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assert Die(descriptor).minimum == expected
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@pytest.mark.parametrize(
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"descriptor,expected",
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[
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pytest.param("d6", 6, id="single"),
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pytest.param("2d6", 12, id="multiple"),
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pytest.param("d12 + 1", 13, id="modifiedsingle"),
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pytest.param("3d12 - 2", 34, id="modifiedmultiple"),
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pytest.param("2d6+3d8-d4+1", 36, id="complex"),
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],
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)
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def test_maximum(descriptor: str, expected: int) -> None:
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"""Test the ``maxiimum`` property"""
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assert Die(descriptor).maximum == expected
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def test_roll_single(mocker: MockerFixture) -> None:
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"""Test rolling a single die"""
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mocked_randint = mocker.patch("gm_assistant.dice.random.randint", return_value=3)
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die = Die("d6")
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assert die.roll() == 3
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mocked_randint.assert_called_once_with(1, 6)
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def test_roll_multiple(mocker: MockerFixture) -> None:
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"""Test rolling multiple of the same die"""
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mocked_randint = mocker.patch("gm_assistant.dice.random.randint", side_effect=[3, 2])
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die = Die("2d6")
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assert die.roll() == 5
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assert mocked_randint.call_count == 2
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mocked_randint.assert_has_calls([mocker.call(1, 6), mocker.call(1, 6)])
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def test_roll_modified_single(mocker: MockerFixture) -> None:
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"""Test rolling a single dice with a modifier"""
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mocked_randint = mocker.patch("gm_assistant.dice.random.randint", return_value=3)
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die = Die("d12+1")
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assert die.roll() == 4
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mocked_randint.assert_called_once_with(1, 12)
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def test_roll_modified_multiple(mocker: MockerFixture) -> None:
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"""Test rolling multiple of the same die with a modifier"""
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mocked_randint = mocker.patch("gm_assistant.dice.random.randint", side_effect=[3, 2])
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die = Die("2d12-1")
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assert die.roll() == 4
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assert mocked_randint.call_count == 2
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mocked_randint.assert_has_calls([mocker.call(1, 12), mocker.call(1, 12)])
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def test_roll_complex(mocker: MockerFixture) -> None:
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"""Test rolling a complex die heap"""
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mocked_randint = mocker.patch("gm_assistant.dice.random.randint", side_effect=[3, 2, 5, 8, 1, 2])
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die = Die("2d6-1+3d8-d4+2")
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assert die.roll() == 18
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assert mocked_randint.call_count == 6
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mocked_randint.assert_has_calls(
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[
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mocker.call(1, 6),
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mocker.call(1, 6),
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mocker.call(1, 8),
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mocker.call(1, 8),
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mocker.call(1, 8),
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mocker.call(1, 4),
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]
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)
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@ -1,11 +0,0 @@
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# SPDX-FileCopyrightText: 2025 2025
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# SPDX-FileContributor: Gergely Polonkai
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#
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# SPDX-License-Identifier: GPL-3.0-or-later
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"""Stub test so the test job doesn’t fail"""
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def test_stub() -> None:
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"""Stub test so the test job doesn’t fail"""
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assert True
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