✨ Allow callers to select Nox sessions in the reusable Python test workflow

[flowerthrower]

Problem Statement

The reusable Python test workflow currently hard-codes the minimums and tests Nox sessions. Callers can select the runner, but cannot reduce the tested Python versions or add a repository-specific expensive session.

Recently the CI load became a bottleneck in MQT repos (due to increased PR activity). MQT Predictor is a concrete example with a very compute-heavy test pipeline. For this reason I would like to reduce its impact on our resources by introducing this Predictor strategy (should be adjusted for other repos):

• Draft pull requests should test only the latest supported Python version on Linux, macOS, and Windows.
• Ready pull requests should test every supported Python version.
• RL/model training should run only once per CI run, on Linux with the latest Python version in ready PRs.

Implementing this entirely in Predictor requires GitHub-specific event handling inside noxfile.py and test selection through exact pytest node IDs. This mixes CI scheduling policy with the local test configuration and is fragile when tests or their dependencies change. Using a complete OS × Python GitHub Actions matrix would make the policy explicit, but would also increase the number of jobs and repeat setup work.

This follows the direction already discussed in #60, where configurable versions and sessions were suggested as a way to reduce redundant CI workload.

Proposed Solution

Add backward-compatible inputs to reusable-python-tests.yml that let callers select the Nox sessions it executes.

One possible interface is:

• minimums-session, defaulting to minimums
• tests-session, defaulting to tests
• an optional additional-session

The caller workflow would own event and runner policy. Consumer repositories would own their test grouping through named Nox sessions and registered pytest markers.

For Predictor, this would allow:

• draft PRs: minimums-<latest> and tests-<latest> on every supported platform;
• ready PRs and non-PR runs: the complete version sessions;
• ready PRs and non-PR runs on Linux/latest only: one additional model-training session.

The exact input interface and realization is open for discussion, because I honestly dont know the implications for other repositories.

[denialhaag]

Another idea that should cover all of your points:

• Combine the current jobs into one. That is, instead of

  workflows/.github/workflows/reusable-python-tests.yml

  Lines 184 to 198 in 9a81217

  	# run the nox minimums session (assumes a nox session named "minimums" exists) with coverage
  	- name: 🐍 Test with minimal versions
  	# `bash` is required so that `$RUNS_ON` is expanded on Windows, too
  	shell: bash
  	env:
  	RUNS_ON: ${{ inputs.runs-on }}
  	run: uvx nox -s minimums --verbose -- --cov --cov-report=xml:coverage-$RUNS_ON.xml --cov-append
  	# run the nox tests session (assumes a nox session named "tests" exists) with coverage
  	- name: 🐍 Test
  	# `bash` is required so that `$RUNS_ON` is expanded on Windows, too
  	shell: bash
  	env:
  	RUNS_ON: ${{ inputs.runs-on }}
  	run: uvx nox -s tests --verbose -- --cov --cov-report=xml:coverage-$RUNS_ON.xml --cov-append

  we have this:

  - if: ${{ !github.event.pull_request.draft }}
    name: 🐍 Test
    shell: bash
    env:
      RUNS_ON: ${{ inputs.runs-on }}
      SESSIONS: ${{ join(fromJSON(inputs.ready-sessions), ' ') }}
    run: uvx nox -s $SESSIONS --verbose -- --cov --cov-report=xml:coverage-$RUNS_ON.xml --cov-append

• As already hinted at in the YAML snippet above, we add a ready-sessions input that defaults to [minimums, tests].

• In addition, we add a second job that runs only for draft PRs. Its sessions are determined by a draft-sessions input. This could, for example, be set to [tests-3.14, minimums-3.14] (or even just [tests-3.14]). I'm not super sure what the default value should be.

This new setup also allows us to make better use of Nox's new parallelization feature, which I'm testing in munich-quantum-toolkit/bench#986. The current setup does not allow us to run minimus and tests sessions in parallel.

@flowerthrower, would this address all of your points? 🤔

[flowerthrower]

Thanks @denialhaag, this should cover it. For the Predictor, I would then do:

• draft-sessions: ["tests-3.14"]
• ready-sessions on macOS and Windows: ["minimums", "tests"]
• ready-sessions on Linux: ["minimums", "tests", "model-training"]

[burgholzer]

Typing this again (shorter this time) because the previous comment got lost in the void:

I like the direction 👍🏼
Combining the sessions makes sense.
I'd probably call it sessions and draft-sessions. (or full-sessions)
Drafts should likely only run latest Python and latest dependencies.

I'd like to extend this to C++ as well.
Coverage and linter should always run.
Drafts may choose to only run debug builds and no release builds on the 6 OS x Arch combinations and may skip the Linux x x86 run that is already covered by the coverage job.

CD may be reduced as well by overriding the cibuildwheel config with Env Vars.

[denialhaag]

I'd probably call it sessions and draft-sessions. (or full-sessions)

I'll go with sessions; sounds way cleaner than ready-sessions!

Drafts should likely only run latest Python and latest dependencies.

Alright, then I'll let it default to tests-3.14 for now. 😌

Drafts may choose to only run debug builds and no release builds on the 6 OS x Arch combinations and may skip the Linux x x86 run that is already covered by the coverage job.

Sounds reasonable!

CD may be reduced as well by overriding the cibuildwheel config with Env Vars.

As the CD is pretty much only triggered when cd.yml is touched, I wouldn't worry about this too much tbh. 🤔