1.0.2: pytest is failing

I know that as twst suite is used now setuptools test however:
+ /usr/bin/python3 -Bm pytest -ra
=========================================================================== test session starts ============================================================================
platform linux -- Python 3.8.9, pytest-6.2.3, py-1.10.0, pluggy-0.13.1
rootdir: /home/tkloczko/rpmbuild/BUILD/mallard-ducktype-1.0.2
plugins: forked-1.3.0, shutil-1.7.0, virtualenv-1.7.0, asyncio-0.14.0, expect-1.1.0, cov-2.11.1, mock-3.5.1, httpbin-1.0.0, xdist-2.2.1, flake8-1.0.7, timeout-1.4.2, betamax-0.8.1, pyfakefs-4.4.0, freezegun-0.4.2, flaky-3.7.0, cases-3.4.6, hypothesis-6.10.1, case-1.5.3, isort-1.3.0
collected 0 items

============================================================================= warnings summary =============================================================================
mallard/ducktype/extensions/_test.py:33
  /home/tkloczko/rpmbuild/BUILD/mallard-ducktype-1.0.2/mallard/ducktype/extensions/_test.py:33: PytestCollectionWarning: cannot collect test class 'TestExtension' because it has a __init__ constructor (from: mallard/ducktype/extensions/_test.py)
    class TestExtension(mallard.ducktype.parser.ParserExtension):

-- Docs: https://docs.pytest.org/en/stable/warnings.html
============================================================================ 1 warning in 0.19s ============================================================================
projectmallard / mallard-ducktype

1.0.2: pytest is failing #19
