test: fix RuntimeWarning in async cluster mode tests

Fix pipeline json mock configuration in AsyncMockRedis and
AsyncMockRedisCluster to properly handle method chaining.
The json().set() and json().get() methods now return the
pipeline object for fluent interface compatibility.

Resolves "coroutine 'AsyncMockMixin._execute_mock_call' was
never awaited" warning in test_async_checkpoint_saver_aput_ttl_behavior.

Author: bsbodden

tests/test_async_cluster_mode.py

@@ -44,9 +44,10 @@ def pipeline(self, transaction=True):
         mock_pipeline.delete = MagicMock(return_value=1)
         mock_pipeline.execute = AsyncMock(return_value=[])
 
-        # Mock json().get() behavior within pipeline
+        # Mock json().set() behavior within pipeline - set must return pipeline for method chaining
         mock_json_pipeline = AsyncMock()
-        mock_json_pipeline.get = MagicMock()
+        mock_json_pipeline.get = MagicMock(return_value=mock_pipeline)
+        mock_json_pipeline.set = MagicMock(return_value=mock_pipeline)
         mock_pipeline.json = MagicMock(return_value=mock_json_pipeline)
         return mock_pipeline
 
@@ -124,8 +125,10 @@ def pipeline(self, transaction=True):
         mock_pipeline.expire = MagicMock(return_value=True)
         mock_pipeline.delete = MagicMock(return_value=1)
 
-        mock_json_pipeline = MagicMock()
-        mock_json_pipeline.get = MagicMock()
+        # Mock json().set() behavior within pipeline - set must return pipeline for method chaining
+        mock_json_pipeline = AsyncMock()
+        mock_json_pipeline.get = MagicMock(return_value=mock_pipeline)
+        mock_json_pipeline.set = MagicMock(return_value=mock_pipeline)
         mock_pipeline.json = MagicMock(return_value=mock_json_pipeline)
         return mock_pipeline