make linter test install testing deps

.github/workflows/test.yml

@@ -32,10 +32,7 @@ jobs:
       with:
         python-version: 3.8
     - name: Install dependencies
-      run: |
-        python -m pip install --upgrade pip
-        python -m pip install pylint flake8 mypy
-        pip install -e .
+      run: pip install -e '.[testing]'
     - name: Lint with pylint
       run: python -m pylint --disable=all -e W0311 --jobs=0 --indent-string='  ' **/*.py
     - name: Lint with flake8