Needy

A tiny library for writing tests that depend on optional packages, without having everything crash when a package you need is just not there…

Installation

Python 3.11+ is required.

pip install pyneedy  # needy was already taken ( ╥_╥)

Quick Start

Define a probe for the optional dependency you want to use, like JAX:

def jax_module() -> None:
    import jax as jax

Then just mark the tests that need it with @needs.to_run(...):

from needy import needs


@needs.to_run(jax_module)
def test_that_uses_jax() -> None:
    import jax.numpy as jnp

    assert jnp.array([1.0, 2.0]).sum() == 3.0

If jax is installed, the test runs. If it isn't, the test is just skipped instead of crashing the whole suite. Yay!

For optional imports at the top of a file (which would normally fail at collection time), use needs.modules(...). See the docs for more.

Documentation

Development

Prerequisites:

• Python >= 3.11
• uv (recommended) or pip
• just (optional, for convenience)

Get set up:

git clone https://gitlab.com/pytooling/needy.git
cd needy
uv sync
uv run pre-commit install

Run all checks (lint, format, type-check, tests):

just check

Or manually:

uv run ruff check --fix && uv run ruff format && uv run pyright && uv run pytest

License

MIT, see LICENSE.