test_history_aware_retriever.py

from langchain_core.documents import Document
from langchain_core.language_models import FakeListLLM
from langchain_core.prompts import PromptTemplate

from langchain.chains import create_history_aware_retriever
from tests.unit_tests.retrievers.parrot_retriever import FakeParrotRetriever


def test_create() -> None:
    answer = "I know the answer!"
    llm = FakeListLLM(responses=[answer])
    retriever = FakeParrotRetriever()
    question_gen_prompt = PromptTemplate.from_template("hi! {input} {chat_history}")
    chain = create_history_aware_retriever(llm, retriever, question_gen_prompt)
    expected_output = [Document(page_content="What is the answer?")]
    output = chain.invoke({"input": "What is the answer?", "chat_history": []})
    assert output == expected_output

    output = chain.invoke({"input": "What is the answer?"})
    assert output == expected_output

    expected_output = [Document(page_content="I know the answer!")]
    output = chain.invoke(
        {"input": "What is the answer?", "chat_history": ["hi", "hi"]}
    )
    assert output == expected_output