Quick start

This walks through installing pytest-conda-solvers and running the bundled suite of conda solver tests against a real solver backend.

Install

Create an environment with conda and a solver backend, then install the plugin from PyPI:

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

pytest-conda-solvers is a pytest plugin, so installing it registers itself automatically — there’s nothing else to configure.

Run the bundled suite

Select a solver backend with --conda-solver. The suite of YAML tests shipped with the package is collected automatically:

pytest --conda-solver=classic

You should see a few hundred tests pass, each one a solver scenario ported from conda’s own test suite (dependency resolution, updates, pinning, conflicts, and more). Run the same suite again against libmamba:

pytest --conda-solver=libmamba

Some tests are restricted to one backend or the other — those show up as SKIPPED rather than failing.

Run a single test

Every test has a human-readable name that becomes its pytest ID. Use -k to run just one while you’re exploring:

pytest --conda-solver=classic -k solve_1_1

Look at what actually ran

solve_1_1 above comes from a YAML file, not Python code. Here it is, roughly:

tests:
  - name: solve_1_1
    id: B001
    kind: solve
    input:
      channels: channel-1
      specs_to_add: numpy
    output:
      final_state:
        - channel-1/${{ arch }}::python-3.3.2-0
        - channel-1/${{ arch }}::numpy-1.7.1-py33_0
        # ...

The plugin reads this file, solves numpy against the bundled channel-1 fixture with whichever solver backend you selected, and asserts that the result matches output.final_state exactly.

Next steps

• Add your own test case: Adding a test

• Look up every field a test case can have: test schema

• Understand what the dataset is and why it exists this way: Conda solver tests and Motivation

• Understand how the plugin collects and runs YAML tests: How the YAML test harness works