use pytest-xdist for running tests in parallel

Author: Tomasz Szymański

.github/workflows/package.yml

@@ -33,7 +33,7 @@ jobs:
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
-        python -m pip install mypy flake8 pytest pytest-cov boto3
+        python -m pip install mypy flake8 pytest pytest-cov pytest-xdist boto3
     - name: Lint with flake8
       run: |
         # stop the build if there are Python syntax errors or undefined names
@@ -43,7 +43,7 @@ jobs:
         mypy ./storages/
     - name: Test with pytest
       run: |
-        python -m pytest --cov-report=xml --cov=storages/
+        python -m pytest -n 5 --cov-report=xml --cov=storages/
     - uses: codecov/codecov-action@v1
       with:
         files: ./coverage.xml