Try to fix mpiexec path windows.

pyproject.toml

@@ -160,10 +160,8 @@ before-test = "python -m pip install impi-rt mpi4py --extra-index-url https://py
 before-all = "python -m pip install impi-rt mpi4py --extra-index-url https://pypi.anaconda.org/mpi4py/simple"
 before-test = [
     "python -m pip install impi-rt mpi4py --extra-index-url https://pypi.anaconda.org/mpi4py/simple",
-    # We need to add venv/libary/bin to the PATH to pick up mpiexec
-    "set PATH=%PATH%;%VIRTUAL_ENV%\\Library\\bin",
-    "echo %PATH%",
 ]
+test-command = "venv-test/library/bin/mpiexec.exe -n 2 python -m mpi4py -m pytest {project}/tests"
 
 [tool.cibuildwheel.macos]
 before-all = ["brew install mpich", ".cibw/build_libomp_macos.sh"]