avoid unix specifc test runner

Author: graingert

tox.ini

@@ -12,7 +12,7 @@ envlist = py37, py38, py39, py310, pypy3
 wheel = True
 wheel_build_env = build
 extras = test
-commands = ./runtests.sh {posargs:tests/}
+commands = pytest -v -s
 
 [testenv:build]
 # empty environment to build universal wheel once per tox invocation