Fix code smell: mock web client

tests/__init__.py

@@ -13,5 +13,5 @@ def client():
     """Set up Flask client for use in tests."""
     app.secret_key = os.urandom(12).hex()
     csrf.init_app(app)
-    client = app.test_client()
-    yield client
+    web_client = app.test_client()
+    yield web_client

tests/test_app.py

@@ -3,7 +3,7 @@
 """Tests for app/app.py"""
 
 
-from tests import client
+from tests import client  # pragma: no cover
 
 
 def test_index(client) -> None: