add coverage

.github/workflows/ci.yaml

@@ -38,7 +38,7 @@ jobs:
       run: |
         python -m pip install --upgrade pip
         pip install -r requirements.txt
-        pip install black flake8 pytest
+        pip install black flake8 pytest-cov
     - name: Run black
       run:
         black --check .
@@ -46,4 +46,4 @@ jobs:
       run: flake8
     - name: Test with pytest
       run:
-          pytest tests
+        pytest tests --cov=enhancer/