langchain/tests/unit_tests/evaluation/comparison/test_eval_chain.py

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"""Test the comparison chains."""
from langchain.evaluation.comparison.eval_chain import PairwiseStringEvalChain
from tests.unit_tests.llms.fake_llm import FakeLLM
def test_pairwise_string_comparison_chain() -> None:
llm = FakeLLM(
queries={
"a": "The values are the same.\n[[C]]",
"b": "A is clearly better than b.\n[[A]]",
"c": "B is clearly better than a.\n[[B]]",
},
sequential_responses=True,
)
chain = PairwiseStringEvalChain.from_llm(llm=llm)
res = chain.evaluate_string_pairs(
output_a="I like pie.",
output_b="I love pie.",
input="What is your favorite food?",
)
assert res["value"] is None
assert res["score"] == 0.5
assert res["reasoning"] == "The values are the same."
res = chain.evaluate_string_pairs(
output_a="I like pie.",
output_b="I like pie.",
input="What is your favorite food?",
)
assert res["value"] == "A"
assert res["score"] == 1
res = chain.evaluate_string_pairs(
output_a="I like pie.",
output_b="I hate pie.",
input="What is your favorite food?",
)
assert res["value"] == "B"
assert res["score"] == 0