Update pythonpackage.yml

Testing method have been changed

.github/workflows/pythonpackage.yml

@@ -30,5 +30,5 @@ jobs:
         flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics
     - name: Test with pytest
       run: |
-        pip install pytest
-        pytest
+        cd tests
+        python runTests.py