Convert test_referencevalidator.py from unittest to pytest

[vladistan]

• Convert class-level setup/teardown to validation_doc pytest fixture
• Convert helper methods to standalone functions (_get_normalizer, _assert_unrepaired_types_the_same)
• Convert all 14 test methods to standalone functions with validation_doc fixture

[codecov[bot]]

Codecov Report

:white_check_mark: All modified and coverable lines are covered by tests. :white_check_mark: Project coverage is 78.41%. Comparing base (f71d115) to head (49218b2).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #452   +/-   ##
=======================================
  Coverage   78.41%   78.41%           
=======================================
  Files          52       52           
  Lines        4536     4536           
  Branches      989      989           
=======================================
  Hits         3557     3557           
  Misses        764      764           
  Partials      215      215           

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

:rocket: New features to boost your workflow:

• :snowflake: Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[ialarmedalien]

I didn't look in detail at all of the tests, but there's a lot of code here that can be converted into pytest parameters instead of iterating through it in the unit test.

[amc-corey-cox]

@vladistan Could you try to get the parametrize work into this PR this week? We'd like to get as many of these PRs merged before our big mono-repo merge between linkml and linkml-runtime @ialarmedalien and @cmungall it looks to me like this at least moves things along in this test file. If @vladistan can't make the requested changes this week, would it be okay to merge this without the improvements requested?

[amc-corey-cox]

I have moved the work for this PR from the contributor fork to the linkml-runtime branch https://github.com/linkml/linkml-runtime/tree/convert-test-reference-validator-to-pytest . These branches will be lifted over in the merge to the mono-repo so you won't lose you work. You will need to open a new PR against the linkml monorepo after the move. I'd prefer to get this in but if we can't please open a new PR when you resume work. Thanks!