Ensure test results directory exists

Add a check to verify the test results directory is successfully created before running tests with pytest. This ensures the test execution environment is properly prepared and prevents potential errors during the test run.

.github/workflows/python-package.yml

@@ -50,5 +50,6 @@ jobs:
         if (Test-Path requirements.txt) { pip install -r requirements.txt }
     - name: Test with pytest
       run: |
-        mkdir src/tests/data/results
+        mkdir -p src/tests/data/results
+        test -d src/tests/data/results || exit 1
         pytest src/tests/