install pytest-mock in github actions

Author: g-simmons

.github/workflows/actions.yml

@@ -21,7 +21,7 @@ jobs:
         run: |
           python -m pip install --upgrade pip
           pip install -e .
-          pip install pytest pytest-asyncio pytest-cov websockets
+          pip install pytest pytest-asyncio pytest-cov pytest-mock websockets
 
       - name: Run tests
         run: |