使用并发参数 pytest -n=2 test.py 命令没有任何问题，但是一旦把 a 和 b 值用随机数生成，并发执行用例就会报错，求解？

def pytest_generate_tests(metafunc):
    if metafunc.cls.__name__ == "TestCase":
            datas = metafunc.cls.datas
            func_args = datas[metafunc.function.__name__]
            keys = sorted(func_args[0])
            metafunc.parametrize(keys, [[func_arg[key] for key in keys] for func_arg in func_args])

import random
# a, b = str(random.randint(0, 10000)), str(random.randint(0, 10000))
a, b = 1, 2

class TestCase:
    datas = {
        "test_01": [
            {"cer_name": a, "name": "小明"}
        ],
        "test_02": [
            {"cer_name": b, "name": "小华"}
        ]
    }

    def test_01(self, cer_name, name):
        assert cer_name == 1

    def test_02(self, cer_name, name):
        assert cer_name == 2