The pytest factoryboy integration we need

conftest.py

from typing import assert_never
from uuid import uuid4

from factory import random as factory_random
from pytest import (
    CallInfo,
    Item,
    StashKey,
    hookimpl,
)


def pytest_addoption(parser):
    parser.addoption("--seed", action="store", help="seed to use for faker")


randomness_seed_stash_key = StashKey[str]()


@hookimpl(tryfirst=True)
def pytest_runtest_setup(item: Item):
    match item.config.getoption("--seed"):
        case None:
            seed = uuid4().hex
        case str() as s:
            seed = s
        case x:
            assert_never(x)  # type: ignore

    factory_random.reseed_random(seed)

    item.stash[randomness_seed_stash_key] = seed


@hookimpl(wrapper=True)
def pytest_runtest_makereport(item: Item, call: CallInfo):
    report = yield
    if report.failed and (seed := item.stash.get(randomness_seed_stash_key, None)):
        report.sections.append(
            (
                "Re-run with same random seed",
                f"pytest {item.nodeid} --seed={seed} to re-run with the same randomness",
            )
        )
    return report

Update: just use pytest-randomly