Add bind_tools on FakeChatModel for development purpose

libs/core/langchain_core/language_models/fake_chat_models.py

@@ -15,7 +15,9 @@ from langchain_core.callbacks import (
 from langchain_core.language_models.chat_models import BaseChatModel, SimpleChatModel
 from langchain_core.messages import AIMessage, AIMessageChunk, BaseMessage
 from langchain_core.outputs import ChatGeneration, ChatGenerationChunk, ChatResult
-from langchain_core.runnables import RunnableConfig
+from langchain_core.runnables import RunnableConfig, Runnable, RunnableLambda
+from langchain_core.tools import BaseTool
+from collections.abc import Sequence, Callable
 
 
 class FakeMessagesListChatModel(BaseChatModel):
@@ -206,6 +208,37 @@ class FakeChatModel(SimpleChatModel):
     def _identifying_params(self) -> dict[str, Any]:
         return {"key": "fake"}
 
+    @override
+    def bind_tools(
+        self,
+        tools: Sequence[Union[dict[str, Any], type, Callable, BaseTool]],
+        *,
+        tool_choice: Optional[str] = None,
+        choice_input: Optional[Union[dict[str, Any], tuple]] = None,
+        **kwargs: Any,
+    ) -> Runnable:
+        def _call_tool_chain(input: dict) -> dict:
+            if tool_choice is None:
+                return {}
+
+            if choice_input is None:
+                raise ValueError(
+                    "choice_input must be provided if tool_choice is specified."
+                )
+
+            tool = next(t for t in tools if t.name == tool_choice)
+
+            params = choice_input if choice_input is not None else input
+
+            if hasattr(tool, "run"):
+                return tool.run(params)
+            else:
+                raise ValueError(
+                    f"Tool {tool} is not callable or does not have a 'run' method."
+                )
+
+        return RunnableLambda(func=_call_tool_chain)
+
 
 class GenericFakeChatModel(BaseChatModel):
     """Generic fake chat model that can be used to test the chat model interface.