fix poetry run pytest command

.github/workflows/main.yml

@@ -32,7 +32,7 @@ jobs:
 
       - name: Test with pytest
         run: |
-          poetry run pytest --cov-report xml:coverage-report/coverage.xml --cov=nbiatoolkit tests/
+          poetry run pytest -n 2 --cov --cov-report xml:coverage-report/coverage.xml
 
       - name: Build documentation
         run: poetry run make html --directory docs/