import hashlib
import numpy as np
import pytest
class Seed:
salt = ""
@classmethod
def generate(cls, uniqueid, extra_salt=""):
"""Generate a unique seed for the given identifier.
The seed should be the same across all machines/platforms.
"""
tohash = uniqueid + cls.salt + extra_salt
sha1 = hashlib.sha1(tohash.encode("utf-8"))
return int(sha1.hexdigest()[:8], 16)
def pytest_addoption(parser):
help_msg = "Specify string to salt `rng` and `seed` fixtures"
parser.addoption("--rng-salt", nargs=1, type=str, help=help_msg)
parser.addini("rng_salt", help=help_msg)
def pytest_configure(config):
cli_salt = config.getoption("--rng-salt", None)
ini_salt = config.getini("rng_salt")
if cli_salt is not None:
Seed.salt = cli_salt[0]
elif ini_salt is not None:
Seed.salt = ini_salt
[docs]@pytest.fixture
def rng(request):
"""A seeded random number generator (RNG).
An instance of `~numpy.random.mtrand.RandomState`. It is preferable
to the unseeded `numpy.random` because it is consistent from one
test run to the next when using the same salt value, and preferable to
a fixed seed RNG because changing the salt checks that tests
are not dependent on a specific seed.
"""
return np.random.RandomState(Seed.generate(request.node.nodeid, extra_salt="rng"))
[docs]@pytest.fixture
def seed(request):
"""An integer random number generator seed in the range [0, 2**32 - 1].
The seed is consistent from one test run to the next
when using the same salt value.
It is preferable to a completely fixed seed because changing the salt
checks that tests are not dependent on a specific seed.
"""
return Seed.generate(request.node.nodeid)
