langchain/tests/unit_tests/chains/test_llm.py

"""Test LLM chain."""
import pytest

from langchain.chains.llm import LLMChain
from langchain.prompts.prompt import PromptTemplate
from tests.unit_tests.llms.fake_llm import FakeLLM


@pytest.fixture
def fake_llm_chain() -> LLMChain:
    """Fake LLM chain for testing purposes."""
    prompt = PromptTemplate(input_variables=["bar"], template="This is a {bar}:")
    return LLMChain(prompt=prompt, llm=FakeLLM(), output_key="text1")


def test_missing_inputs(fake_llm_chain: LLMChain) -> None:
    """Test error is raised if inputs are missing."""
    with pytest.raises(ValueError):
        fake_llm_chain({"foo": "bar"})


def test_valid_call(fake_llm_chain: LLMChain) -> None:
    """Test valid call of LLM chain."""
    output = fake_llm_chain({"bar": "baz"})
    assert output == {"bar": "baz", "text1": "foo"}

    # Test with stop words.
    output = fake_llm_chain({"bar": "baz", "stop": ["foo"]})
    # Response should be `bar` now.
    assert output == {"bar": "baz", "stop": ["foo"], "text1": "bar"}


def test_predict_method(fake_llm_chain: LLMChain) -> None:
    """Test predict method works."""
    output = fake_llm_chain.predict(bar="baz")
    assert output == "foo"