TestChainModelCallHandlers Class — langchain Architecture
Architecture documentation for the TestChainModelCallHandlers class in test_composition.py from the langchain codebase.
Entity Profile
Dependency Diagram
graph TD 5e72c447_c04a_d317_225b_afa4d498b59e["TestChainModelCallHandlers"] e8d75ab8_cc79_e047_2101_0ea8e47809e6["_ComposedExtendedModelResponse"] 5e72c447_c04a_d317_225b_afa4d498b59e -->|extends| e8d75ab8_cc79_e047_2101_0ea8e47809e6 529538f3_9470_dbd3_2a47_9e95e11a4afe["test_composition.py"] 5e72c447_c04a_d317_225b_afa4d498b59e -->|defined in| 529538f3_9470_dbd3_2a47_9e95e11a4afe d7da206d_6194_e663_cffc_1a6149fe3047["test_empty_handlers_returns_none()"] 5e72c447_c04a_d317_225b_afa4d498b59e -->|method| d7da206d_6194_e663_cffc_1a6149fe3047 30869bdc_14b4_affc_afd0_7aa8d1b64dc7["test_single_handler_returns_unchanged()"] 5e72c447_c04a_d317_225b_afa4d498b59e -->|method| 30869bdc_14b4_affc_afd0_7aa8d1b64dc7 d48098ee_abf9_680f_f095_b00ba3ff95fb["test_two_handlers_basic_composition()"] 5e72c447_c04a_d317_225b_afa4d498b59e -->|method| d48098ee_abf9_680f_f095_b00ba3ff95fb 9571a66f_3cfc_fb64_879e_3904d5ef8907["test_two_handlers_with_commands()"] 5e72c447_c04a_d317_225b_afa4d498b59e -->|method| 9571a66f_3cfc_fb64_879e_3904d5ef8907 e7ef9e7c_7cac_65af_270c_7a6b7507aa10["test_three_handlers_composition()"] 5e72c447_c04a_d317_225b_afa4d498b59e -->|method| e7ef9e7c_7cac_65af_270c_7a6b7507aa10 5b594f23_684f_e87d_2e3a_0e9fb2102257["test_inner_handler_retry()"] 5e72c447_c04a_d317_225b_afa4d498b59e -->|method| 5b594f23_684f_e87d_2e3a_0e9fb2102257 fb071b18_f4bf_e841_c09c_bea353d5e793["test_error_to_success_conversion()"] 5e72c447_c04a_d317_225b_afa4d498b59e -->|method| fb071b18_f4bf_e841_c09c_bea353d5e793 630dd632_c630_42c1_703e_e565a3711b57["test_request_modification()"] 5e72c447_c04a_d317_225b_afa4d498b59e -->|method| 630dd632_c630_42c1_703e_e565a3711b57 e66fea12_e10b_1f15_92c0_d237f0b1cff1["test_composition_preserves_state_and_runtime()"] 5e72c447_c04a_d317_225b_afa4d498b59e -->|method| e66fea12_e10b_1f15_92c0_d237f0b1cff1 d5463e49_cba1_1c30_cf32_ff569b0404f6["test_multiple_yields_in_retry_loop()"] 5e72c447_c04a_d317_225b_afa4d498b59e -->|method| d5463e49_cba1_1c30_cf32_ff569b0404f6
Relationship Graph
Source Code
libs/langchain_v1/tests/unit_tests/agents/middleware/core/test_composition.py lines 40–349
class TestChainModelCallHandlers:
"""Test the `_chain_model_call_handlers` composition function."""
def test_empty_handlers_returns_none(self) -> None:
"""Test that empty handlers list returns None."""
result = _chain_model_call_handlers([])
assert result is None
def test_single_handler_returns_unchanged(self) -> None:
"""Test that single handler is wrapped to normalize output."""
def handler(
request: ModelRequest, base_handler: Callable[[ModelRequest], ModelResponse]
) -> ModelResponse:
return base_handler(request)
result = _chain_model_call_handlers([handler])
# Result is wrapped to normalize, so it won't be identical
assert result is not None
assert callable(result)
def test_two_handlers_basic_composition(self) -> None:
"""Test basic composition of two handlers."""
execution_order = []
def outer(
request: ModelRequest, handler: Callable[[ModelRequest], ModelResponse]
) -> ModelResponse:
execution_order.append("outer-before")
result = handler(request)
execution_order.append("outer-after")
return result
def inner(
request: ModelRequest, handler: Callable[[ModelRequest], ModelResponse]
) -> ModelResponse:
execution_order.append("inner-before")
result = handler(request)
execution_order.append("inner-after")
return result
composed = _chain_model_call_handlers([outer, inner])
assert composed is not None
result = composed(create_test_request(), create_mock_base_handler())
assert execution_order == [
"outer-before",
"inner-before",
"inner-after",
"outer-after",
]
# Outermost result is always _ComposedExtendedModelResponse
assert isinstance(result, _ComposedExtendedModelResponse)
assert result.model_response.result[0].content == "test"
def test_two_handlers_with_commands(self) -> None:
"""Test that commands from inner and outer are collected correctly."""
def outer(
request: ModelRequest, handler: Callable[[ModelRequest], ModelResponse]
) -> ExtendedModelResponse:
response = handler(request)
return ExtendedModelResponse(
model_response=response,
command=Command(update={"outer_key": "outer_val"}),
)
def inner(
request: ModelRequest, handler: Callable[[ModelRequest], ModelResponse]
) -> ExtendedModelResponse:
response = handler(request)
return ExtendedModelResponse(
model_response=response,
command=Command(update={"inner_key": "inner_val"}),
)
composed = _chain_model_call_handlers([outer, inner])
assert composed is not None
result = composed(create_test_request(), create_mock_base_handler())Extends
Source
Frequently Asked Questions
What is the TestChainModelCallHandlers class?
TestChainModelCallHandlers is a class in the langchain codebase, defined in libs/langchain_v1/tests/unit_tests/agents/middleware/core/test_composition.py.
Where is TestChainModelCallHandlers defined?
TestChainModelCallHandlers is defined in libs/langchain_v1/tests/unit_tests/agents/middleware/core/test_composition.py at line 40.
What does TestChainModelCallHandlers extend?
TestChainModelCallHandlers extends _ComposedExtendedModelResponse.
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