diff --git a/gnes/composer/base.py b/gnes/composer/base.py
index 3534e75d..1fcac2ef 100644
--- a/gnes/composer/base.py
+++ b/gnes/composer/base.py
@@ -156,10 +156,10 @@ def build_layers(self) -> List['YamlComposer.Layer']:
             last_layer = self._layers[idx - 1]
             for l in self._add_router(last_layer, layer):
                 all_layers.append(copy.deepcopy(l))
-        # # add frontend
-        # for l in self._add_router(all_layers[-1], all_layers[0]):
-        #     all_layers.append(copy.deepcopy(l))
         all_layers[0] = copy.deepcopy(self._layers[0])
+
+        # gRPCfrontend should always on the bind role
+
         return all_layers
 
     @staticmethod
diff --git a/tests/test_image_encoder.py b/tests/test_image_encoder.py
index 5582d039..82917678 100644
--- a/tests/test_image_encoder.py
+++ b/tests/test_image_encoder.py
@@ -4,7 +4,7 @@
 import zipfile
 
 from gnes.encoder.image.base import BasePytorchEncoder
-from gnes.preprocessor.base import BaseUnaryPreprocessor
+from gnes.preprocessor.base import BaseUnaryPreprocessor, PipelinePreprocessor
 from gnes.preprocessor.image.resize import ResizeChunkPreprocessor
 from gnes.preprocessor.image.sliding_window import VanillaSlidingPreprocessor
 from gnes.proto import gnes_pb2, blob2array
@@ -20,8 +20,10 @@ def img_process_for_test(dirname):
         test_img.append(d)
 
     test_img_all_preprocessor = []
-    for preprocessor in [BaseUnaryPreprocessor(doc_type=gnes_pb2.Document.IMAGE),
-                         ResizeChunkPreprocessor(),
+    pipline_prep1 = PipelinePreprocessor()
+    pipline_prep1.component = lambda: [BaseUnaryPreprocessor(doc_type=gnes_pb2.Document.IMAGE),
+                                       ResizeChunkPreprocessor()]
+    for preprocessor in [pipline_prep1,
                          VanillaSlidingPreprocessor()]:
         test_img_copy = copy.deepcopy(test_img)
         for img in test_img_copy: