add mock for encoder in new tests

tests/unit/test_layer.py

 import os
 import pytest
-from unittest.mock import mock_open, patch
+from unittest.mock import Mock, mock_open, patch
 
 from semantic_router.encoders import BaseEncoder, CohereEncoder, OpenAIEncoder
 from semantic_router.layer import LayerConfig, RouteLayer
@@ -177,22 +177,24 @@ class TestRouteLayer:
         route_layer = RouteLayer(encoder=openai_encoder, routes=routes)
         route_layer.to_json("test_output.json")
         assert os.path.exists("test_output.json")
-        route_layer_from_file = RouteLayer.from_json("test_output.json")
-        assert (
-            route_layer_from_file.index is not None
-            and route_layer_from_file.categories is not None
-        )
+        with patch("semantic_router.schema.Encoder", new_callable=Mock):
+            route_layer_from_file = RouteLayer.from_json("test_output.json")
+            assert (
+                route_layer_from_file.index is not None
+                and route_layer_from_file.categories is not None
+            )
         os.remove("test_output.json")
 
     def test_yaml(self, openai_encoder, routes):
         route_layer = RouteLayer(encoder=openai_encoder, routes=routes)
         route_layer.to_yaml("test_output.yaml")
         assert os.path.exists("test_output.yaml")
-        route_layer_from_file = RouteLayer.from_yaml("test_output.yaml")
-        assert (
-            route_layer_from_file.index is not None
-            and route_layer_from_file.categories is not None
-        )
+        with patch("semantic_router.schema.Encoder", new_callable=Mock):
+            route_layer_from_file = RouteLayer.from_yaml("test_output.yaml")
+            assert (
+                route_layer_from_file.index is not None
+                and route_layer_from_file.categories is not None
+            )
         os.remove("test_output.yaml")
 
     def test_config(self, openai_encoder, routes):
@@ -200,11 +202,12 @@ class TestRouteLayer:
         # confirm route creation functions as expected
         layer_config = route_layer.to_config()
         assert layer_config.routes == routes
-        # now load from config and confirm it's the same
-        route_layer_from_config = RouteLayer.from_config(layer_config)
-        assert (route_layer_from_config.index == route_layer.index).all()
-        assert (route_layer_from_config.categories == route_layer.categories).all()
-        assert route_layer_from_config.score_threshold == route_layer.score_threshold
+        with patch("semantic_router.schema.Encoder", new_callable=Mock):
+            # now load from config and confirm it's the same
+            route_layer_from_config = RouteLayer.from_config(layer_config)
+            assert (route_layer_from_config.index == route_layer.index).all()
+            assert (route_layer_from_config.categories == route_layer.categories).all()
+            assert route_layer_from_config.score_threshold == route_layer.score_threshold
 
 
 # Add more tests for edge cases and error handling as needed.