Add a conformance test workflow

[jku]

• The conformance test suite is likely to still change quite a bit so the workflow is not enabled on PRs yet (and does not pin the action version)
• The actual conformance client is copied from the tuf-conformance project
• This is mostly a test to see how things should work out, and a demonstration of how the tuf-conformance project should be used

[coveralls]

Pull Request Test Coverage Report for Build 9894255152

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 96.805%

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Totals
Change from base Build 9858741524:	0.0%
Covered Lines:	1554
Relevant Lines:	1591

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💛 - Coveralls

[jku]

There is no automated way to run he conformance test suite locally (using your local python-tuf version) but we could potentially add something into tox... it will need a bit of thinking though.

It's not too difficult manually, something like this should work:

pip install -e $CONFORMANCE_SUITE_DIR -e $PYTHON_TUF_DIR
pytest "$CONFORMANCE_SUITE_DIR/tuf_conformance" --entrypoint $PYTHON_TUF_DIR/.github/scripts/conformance-client.py

[lukpueh]

Very cool. Tried it locally and it worked nicely. Does the action also work with tuf-confromance@main? AFAICS you tried it against a patched action?
https://github.com/jku/python-tuf/actions/runs/9874869528

[lukpueh]

nit: We don't call it wrapper elsewhere here. IMO calling it conformance client would be clearer.

[jku]

Yeah I used the patched branch for testing but that branch has since been merged -- main should work right now (obviously it will break at some point so we should start pinning the action as soon as we have something that looks like a release)