Install pytest for testing

.github/workflows/main.yml

@@ -111,7 +111,7 @@ jobs:
         run: |
           python -m pip install --upgrade pip
           pip install -e pixl_core
-          pip install -e pixl_dcmd
+          pip install -e pixl_dcmd[test]
 
       - name: Run tests
         working-directory: pixl_dcmd