Files
langchain/libs/standard-tests
Mason Daugherty 43880362d8 feat(standard-tests): validate tool call chunks during streaming (#34707)
As a LangChain user streaming a tool-calling model, I expect each
streamed chunk to expose structured `tool_call_chunk` content blocks so
I can render or process tool calls live, instead of waiting for the
final aggregated message.

This adds `tool_call_streaming` to `ModelProfile` and uses it in the
standard chat-model tool-calling tests. When a model profile opts in,
`test_tool_calling` and `test_tool_calling_async` now validate that at
least one streamed chunk includes a `tool_call_chunk` block via
`content_blocks`, while preserving the existing final-message
validation.

This keeps the contract profile-gated so providers can opt in once their
streaming chunk shape is verified. This PR opts in the providers
verified by smoke testing with straightforward profile coverage: OpenAI,
Anthropic, Fireworks, HuggingFace, OpenRouter, DeepSeek, and xAI. The
generated profile artifacts are refreshed so runtime profiles expose the
new capability flag.

Perplexity Responses also passed the smoke test, but its current profile
data is for the `sonar` family while the Responses smoke path used a
routed model string. That profile strategy is left as follow-up.
MistralAI currently streams `.tool_call_chunks`, but its content-block
translator exposes a complete `tool_call` block instead of
`tool_call_chunk`, so it also stays out of this flag until that
integration is fixed.
2026-06-10 22:29:02 -04:00
..

🦜🔗 langchain-tests

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Looking for the JS/TS version? Check out LangChain.js.

Quick Install

pip install langchain-tests

🤔 What is this?

This is a testing library for LangChain integrations. It contains the base classes for a standard set of tests.

📖 Documentation

For full documentation, see the API reference.

📕 Releases & Versioning

See our Releases and Versioning policies.

We encourage pinning your version to a specific version in order to avoid breaking your CI when we publish new tests. We recommend upgrading to the latest version periodically to make sure you have the latest tests.

Not pinning your version will ensure you always have the latest tests, but it may also break your CI if we introduce tests that your integration doesn't pass.

💁 Contributing

As an open-source project in a rapidly developing field, we are extremely open to contributions, whether it be in the form of a new feature, improved infrastructure, or better documentation.

For detailed information on how to contribute, see the Contributing Guide.

Usage

To add standard tests to an integration package (e.g., for a chat model), you need to create

  1. A unit test class that inherits from ChatModelUnitTests
  2. An integration test class that inherits from ChatModelIntegrationTests

tests/unit_tests/test_standard.py:

"""Standard LangChain interface tests"""

from typing import Type

import pytest
from langchain_core.language_models import BaseChatModel
from langchain_tests.unit_tests import ChatModelUnitTests

from langchain_parrot_chain import ChatParrotChain


class TestParrotChainStandard(ChatModelUnitTests):
    @pytest.fixture
    def chat_model_class(self) -> Type[BaseChatModel]:
        return ChatParrotChain

tests/integration_tests/test_standard.py:

"""Standard LangChain interface tests"""

from typing import Type

import pytest
from langchain_core.language_models import BaseChatModel
from langchain_tests.integration_tests import ChatModelIntegrationTests

from langchain_parrot_chain import ChatParrotChain


class TestParrotChainStandard(ChatModelIntegrationTests):
    @pytest.fixture
    def chat_model_class(self) -> Type[BaseChatModel]:
        return ChatParrotChain

Reference

The following fixtures are configurable in the test classes. Anything not marked as required is optional.

  • chat_model_class (required): The class of the chat model to be tested
  • chat_model_params: The keyword arguments to pass to the chat model constructor
  • chat_model_has_tool_calling: Whether the chat model can call tools. By default, this is set to hasattr(chat_model_class, 'bind_tools)
  • chat_model_has_structured_output: Whether the chat model can structured output. By default, this is set to hasattr(chat_model_class, 'with_structured_output')