Pytest-rng released

The Nengo team at ABR is excited to announce the first release of pytest-rng. pytest-rng is made available under the open source MIT license so that all Python projects can make use of it to better test their numerical code.

What is pytest-rng?

pytest-rng ensures that “randomness” in your tests is reproducible from one run to the next by providing rng and seed fixtures for pytest.

Use the rng fixture to get a pre-seeded random number generator (RNG) that exposes NumPy’s RandomState interface.

import numpy as np

def test_with_randomness(rng):
    """Print the same three numbers every time."""
    print(rng.uniform(-1, 1), size=3))

Use the seed fixture to get an integer seed that can be used to initialize your own RNG.

import numpy as np

def test_with_randomness(seed):
    """Print the same four numbers every time."""
    rng = np.random.RandomState(seed)
    print(rng.uniform(-1, 1), size=3))

In order to ensure that your tests are robust to different seeds, you can change all of the seeds across all of your tests by specifying a salt value. You can do this either in a configuration file like setup.cfg or pytest.ini

rng_salt = v0.3.0

or via the command line

pytest --rng-salt "v0.4.0"

How do I use it?

To use the fixture, first install it with pip:

pip install pytest-rng

then you can use it in your tests by putting rng or seed in the function signature, like other pytest fixtures. We recommend you add pytest-rng your list of test requirements as well.

Where can I learn more?

For more details and advanced usage, see the full documentation.

Where can I get help?

If you have any questions, run into any bugs, or have suggestions for new features, please file an issue on Github.