tests: convert to pytest idioms #55

Job	Run time
Validate coverage	30s
Build the documentation	25s
Lint the package	28s
Python: 3.8-x64 on ubuntu-latest	31s
Python: 3.8-x64 on windows-latest	54s
Python: 3.8-x86 on windows-latest	1m 7s
Python: 3.8-x64 on macos-11	1s
Python: 3.9-x64 on ubuntu-latest	28s
Python: 3.9-x64 on windows-latest	47s
Python: 3.9-x86 on windows-latest	1m 4s
Python: 3.9-x64 on macos-11	1s
Python: 3.10-x64 on ubuntu-latest	20s
Python: 3.10-x64 on windows-latest	1m 0s
Python: 3.10-x86 on windows-latest	1m 7s
Python: 3.10-x64 on macos-11	1s
Python: 3.11-x64 on ubuntu-latest	39s
Python: 3.11-x64 on windows-latest	46s
Python: 3.11-x86 on windows-latest	1m 2s
Python: 3.11-x64 on macos-11	1s
Python: 3.12-x64 on ubuntu-latest	42s
Python: 3.12-x64 on windows-latest	54s
Python: 3.12-x86 on windows-latest	1m 17s
Python: 3.12-x64 on macos-11	1s
Python: pypy-3.8-x64 on ubuntu-latest	1m 8s
Python: pypy-3.8-x64 on windows-latest	1m 55s
Python: pypy-3.8-x86 on windows-latest	1m 53s
Python: pypy-3.8-x64 on macos-11	1s
	19m 3s

Provide feedback