standard tests: add test for tool calling (#23234)

Including streaming

libs/standard-tests/langchain_standard_tests/integration_tests/chat_models.py

@@ -1,10 +1,18 @@
 import base64
 import json
+from typing import Optional
 
 import httpx
 import pytest
 from langchain_core.language_models import BaseChatModel
-from langchain_core.messages import AIMessage, AIMessageChunk, HumanMessage, ToolMessage
+from langchain_core.messages import (
+    AIMessage,
+    AIMessageChunk,
+    BaseMessageChunk,
+    HumanMessage,
+    ToolMessage,
+)
+from langchain_core.tools import tool
 
 from langchain_standard_tests.unit_tests.chat_models import (
     ChatModelTests,
@@ -12,6 +20,21 @@ from langchain_standard_tests.unit_tests.chat_models import (
 )
 
 
+@tool
+def magic_function(input: int) -> int:
+    """Applies a magic function to an input."""
+    return input + 2
+
+
+def _validate_tool_call_message(message: AIMessage) -> None:
+    assert isinstance(message, AIMessage)
+    assert len(message.tool_calls) == 1
+    tool_call = message.tool_calls[0]
+    assert tool_call["name"] == "magic_function"
+    assert tool_call["args"] == {"input": 3}
+    assert tool_call["id"] is not None
+
+
 class ChatModelIntegrationTests(ChatModelTests):
     def test_invoke(self, model: BaseChatModel) -> None:
         result = model.invoke("Hello")
@@ -98,6 +121,24 @@ class ChatModelIntegrationTests(ChatModelTests):
         result = custom_model.invoke("hi")
         assert isinstance(result, AIMessage)
 
+    def test_tool_calling(self, model: BaseChatModel) -> None:
+        if not self.has_tool_calling:
+            pytest.skip("Test requires tool calling.")
+        model_with_tools = model.bind_tools([magic_function])
+
+        # Test invoke
+        query = "What is the value of magic_function(3)? Use the tool."
+        result = model_with_tools.invoke(query)
+        assert isinstance(result, AIMessage)
+        _validate_tool_call_message(result)
+
+        # Test stream
+        full: Optional[BaseMessageChunk] = None
+        for chunk in model_with_tools.stream(query):
+            full = chunk if full is None else full + chunk  # type: ignore
+        assert isinstance(full, AIMessage)
+        _validate_tool_call_message(full)
+
     def test_tool_message_histories_string_content(
         self,
         model: BaseChatModel,