langchain/tests/unit_tests/prompts/test_chat.py

from typing import List

from langchain.prompts import PromptTemplate
from langchain.prompts.chat import (
    AIMessagePromptTemplate,
    BaseMessagePromptTemplate,
    ChatMessagePromptTemplate,
    ChatPromptTemplate,
    ChatPromptValue,
    HumanMessagePromptTemplate,
    SystemMessagePromptTemplate,
)
from langchain.schema import HumanMessage


def create_messages() -> List[BaseMessagePromptTemplate]:
    """Create messages."""
    system_message_prompt = SystemMessagePromptTemplate(
        prompt=PromptTemplate(
            template="Here's some context: {context}",
            input_variables=["context"],
        )
    )
    human_message_prompt = HumanMessagePromptTemplate(
        prompt=PromptTemplate(
            template="Hello {foo}, I'm {bar}. Thanks for the {context}",
            input_variables=["foo", "bar", "context"],
        )
    )
    ai_message_prompt = AIMessagePromptTemplate(
        prompt=PromptTemplate(
            template="I'm an AI. I'm {foo}. I'm {bar}.",
            input_variables=["foo", "bar"],
        )
    )
    chat_message_prompt = ChatMessagePromptTemplate(
        role="test",
        prompt=PromptTemplate(
            template="I'm a generic message. I'm {foo}. I'm {bar}.",
            input_variables=["foo", "bar"],
        ),
    )
    return [
        system_message_prompt,
        human_message_prompt,
        ai_message_prompt,
        chat_message_prompt,
    ]


def create_chat_prompt_template() -> ChatPromptTemplate:
    """Create a chat prompt template."""
    return ChatPromptTemplate(
        input_variables=["foo", "bar", "context"],
        messages=create_messages(),
    )


def test_chat_prompt_template() -> None:
    """Test chat prompt template."""
    prompt_template = create_chat_prompt_template()
    prompt = prompt_template.format_prompt(foo="foo", bar="bar", context="context")
    assert isinstance(prompt, ChatPromptValue)
    messages = prompt.to_messages()
    assert len(messages) == 4
    assert messages[0].content == "Here's some context: context"
    assert messages[1].content == "Hello foo, I'm bar. Thanks for the context"
    assert messages[2].content == "I'm an AI. I'm foo. I'm bar."
    assert messages[3].content == "I'm a generic message. I'm foo. I'm bar."

    string = prompt.to_string()
    expected = (
        "System: Here's some context: context\n"
        "Human: Hello foo, I'm bar. Thanks for the context\n"
        "AI: I'm an AI. I'm foo. I'm bar.\n"
        "test: I'm a generic message. I'm foo. I'm bar."
    )
    assert string == expected

    string = prompt_template.format(foo="foo", bar="bar", context="context")
    assert string == expected


def test_chat_prompt_template_from_messages() -> None:
    """Test creating a chat prompt template from messages."""
    chat_prompt_template = ChatPromptTemplate.from_messages(create_messages())
    assert sorted(chat_prompt_template.input_variables) == sorted(
        ["context", "foo", "bar"]
    )
    assert len(chat_prompt_template.messages) == 4


def test_chat_prompt_template_with_messages() -> None:
    messages = create_messages() + [HumanMessage(content="foo")]
    chat_prompt_template = ChatPromptTemplate.from_messages(messages)
    assert sorted(chat_prompt_template.input_variables) == sorted(
        ["context", "foo", "bar"]
    )
    assert len(chat_prompt_template.messages) == 5
    prompt_value = chat_prompt_template.format_prompt(
        context="see", foo="this", bar="magic"
    )
    prompt_value_messages = prompt_value.to_messages()
    assert prompt_value_messages[-1] == HumanMessage(content="foo")