Update win-build-and-pytest.yml

.github/workflows/win-build-and-pytest.yml

@@ -26,7 +26,7 @@ jobs:
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
-        pip install flake8 pytest
+        pip install flake8 pytest pytest-cov
         pip install wheel
         python setup.py sdist bdist_wheel
         pip install dist/*.whl