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fix: ensure deterministic behavior for Use function with seeded random #2

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@priyankc priyankc commented Jun 10, 2025

Description

Fixes the random state handling in the Use function to ensure it respects the seeded random instance from ModelFactory.seed_random().

Testing

Added a unit test to repro and fix.

Before the fix

((.venv) ) ➜  polyfactory git:(workback-fix-580) ✗ pytest tests/test_random_seed.py
=============================================== test session starts ================================================
platform darwin -- Python 3.12.10, pytest-8.4.0, pluggy-1.6.0
rootdir: /Users/priyank/OSS/polyfactory
configfile: pyproject.toml
plugins: hypothesis-6.135.4, Faker-37.3.0, cov-6.1.1, asyncio-1.0.0
asyncio: mode=Mode.AUTO, asyncio_default_fixture_loop_scope=function, asyncio_default_test_loop_scope=function
collected 4 items

tests/test_random_seed.py .F..                                                                               [100%]

===================================================== FAILURES =====================================================
_____________________________________ test_deterministic_use_function_seeding ______________________________________

    def test_deterministic_use_function_seeding():
        class MyModel(BaseModel):
            choice_value: str

        choices = ["option1", "option2", "option3", "option4", "option5"]

        class MyModelFactory(ModelFactory):
            __model__ = MyModel
            choice_value = Use(ModelFactory.__random__.choice, choices)

        ModelFactory.seed_random(12345)
        first_batch = [MyModelFactory.build().choice_value for _ in range(10)]


        ModelFactory.seed_random(12345) # Seed random again with the same value
        second_batch = [MyModelFactory.build().choice_value for _ in range(10)]

>       assert first_batch == second_batch
E       AssertionError: assert ['option2', '...option5', ...] == ['option2', '...option4', ...]
E
E         At index 1 diff: 'option3' != 'option4'
E         Use -v to get more diff

tests/test_random_seed.py:46: AssertionError
============================================= short test summary info ==============================================
FAILED tests/test_random_seed.py::test_deterministic_use_function_seeding - AssertionError: assert ['option2', '...option5', ...] == ['option2', '...option4', ...]
=========================================== 1 failed, 3 passed in 0.42s ============================================

After the fix

((.venv) ) ➜  polyfactory git:(workback-fix-580) ✗ pytest tests/test_random_seed.py
=============================================== test session starts ================================================
platform darwin -- Python 3.12.10, pytest-8.4.0, pluggy-1.6.0
rootdir: /Users/priyank/OSS/polyfactory
configfile: pyproject.toml
plugins: hypothesis-6.135.4, Faker-37.3.0, cov-6.1.1, asyncio-1.0.0
asyncio: mode=Mode.AUTO, asyncio_default_fixture_loop_scope=function, asyncio_default_test_loop_scope=function
collected 4 items

tests/test_random_seed.py ....                                                                               [100%]

================================================ 4 passed in 0.37s =================================================

Closes

Fixes: litestar-org#580

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Bug: unexpected behavior with seed_random
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