Fix where coverage starts

.github/workflows/tests.yml

@@ -103,6 +103,6 @@ jobs:
       - name: Install project and its dependencies
         run: poetry install
       - name: Build coverage file
-        run: poetry run pytest --cache-clear --cov --cov-report xml tests
+        run: poetry run pytest --cache-clear --cov src --cov-report xml tests
       - name: Upload coverage reports to Codecov with GitHub Action
         uses: codecov/codecov-action@v2