pytest-conda-solvers

A pytest plugin that runs shared conda solver YAML tests against classic, libmamba, or other conda solver backends.

The PyPI package ships the plugin, fixtures, mock channel data, and shared YAML suite under pytest_conda_solvers/. When the plugin loads, it automatically adds the bundled suite to pytest's collection.

conda-solver-tests pytest plugin was orginally generated with [Cookiecutter] along with [@hackebrot]'s [cookiecutter-pytest-plugin] template.

Error assertion semantics

For unsatisfiable tests, this suite deliberately asserts more than conda's own test suite does when running under conda-libmamba-solver. Upstream's assert_unsatisfiable helper only checks the exception is an UnsatisfiableError subclass there, because its entries comparison is gated on the exact UnsatisfiableError type. Our runner additionally checks that the endpoint package names of each expected conflict chain appear in the libmamba error message, and message_includes/message_excludes fields in the YAML add further content checks. This strengthening is intentional: cross-solver consistency of error reporting is part of what this plugin exists to verify.

Requirements

• Python ≥ 3.10
• A working conda (>=26.3.0) installation in the environment (install via conda, mamba, or pixi — not from PyPI)
• The solver backend under test (for example conda-libmamba-solver)

Installation

conda create -n solver-test-env conda conda-libmamba-solver pip
conda activate solver-test-env
python -m pip install pytest-conda-solvers

For local development from a checkout:

pixi install
# or: pip install -e .

Usage

Select a solver with --conda-solver; the bundled suite is collected automatically:

pytest --conda-solver=libmamba
pytest --conda-solver=classic

Paths passed to pytest are collected alongside the bundled suite, so solver authors can add their own Python or YAML tests normally.

Use --no-bundled-solver-tests to collect custom tests without the suite shipped by this package.

From this repository with pixi:

pixi run test-libmamba-solver
pixi run test-classic-solver

The plugin collects solver-suite .yaml files, starts a session-scoped mock channel server, and runs each case through the selected solver backend.

Contributing

Contributions are welcome. It is recommended to use pixi for the development environment and run the solver test tasks above before opening a pull request.

Build the documentation locally with pixi run -e docs docs-build.

License

Distributed under the BSD-3-Clause license.

Issues

If you encounter problems, please file an issue.