Convert to pytest

[weiwei]

The command line conversion tools didn't work, but Copilot works quite good for converting individual cases. Probably the only good case to justify me buying it. Still a lot of manual copy/paste though.

Some cases are rewritten to use parametrize.

[codecov]

Codecov Report

Patch coverage: 99.72% and no project coverage change.

Comparison is base (5648005) 98.24% compared to head (96b51b2) 98.24%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #109   +/-   ##
=======================================
  Coverage   98.24%   98.24%           
=======================================
  Files           8        8           
  Lines        1424     1428    +4     
=======================================
+ Hits         1399     1403    +4     
  Misses         25       25           

Impacted Files	Coverage Δ
tests/test_general.py	99.12% <99.41%> (+<0.01%)	⬆️
tests/test_cli.py	100.00% <100.00%> (ø)
tests/test_fromfile.py	98.75% <100.00%> (ø)
tests/test_xunit2.py	100.00% <100.00%> (ø)

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