langchain/tests/unit_tests/test_text_splitter.py

"""Test text splitting functionality."""
import pytest

from langchain.docstore.document import Document
from langchain.text_splitter import (
    CharacterTextSplitter,
    RecursiveCharacterTextSplitter,
)


def test_character_text_splitter() -> None:
    """Test splitting by character count."""
    text = "foo bar baz 123"
    splitter = CharacterTextSplitter(separator=" ", chunk_size=7, chunk_overlap=3)
    output = splitter.split_text(text)
    expected_output = ["foo bar", "bar baz", "baz 123"]
    assert output == expected_output


def test_character_text_splitter_empty_doc() -> None:
    """Test splitting by character count doesn't create empty documents."""
    text = "foo  bar"
    splitter = CharacterTextSplitter(separator=" ", chunk_size=2, chunk_overlap=0)
    output = splitter.split_text(text)
    expected_output = ["foo", "bar"]
    assert output == expected_output


def test_character_text_splitter_separtor_empty_doc() -> None:
    """Test edge cases are separators."""
    text = "f b"
    splitter = CharacterTextSplitter(separator=" ", chunk_size=2, chunk_overlap=0)
    output = splitter.split_text(text)
    expected_output = ["f", "b"]
    assert output == expected_output


def test_character_text_splitter_long() -> None:
    """Test splitting by character count on long words."""
    text = "foo bar baz a a"
    splitter = CharacterTextSplitter(separator=" ", chunk_size=3, chunk_overlap=1)
    output = splitter.split_text(text)
    expected_output = ["foo", "bar", "baz", "a a"]
    assert output == expected_output


def test_character_text_splitter_short_words_first() -> None:
    """Test splitting by character count when shorter words are first."""
    text = "a a foo bar baz"
    splitter = CharacterTextSplitter(separator=" ", chunk_size=3, chunk_overlap=1)
    output = splitter.split_text(text)
    expected_output = ["a a", "foo", "bar", "baz"]
    assert output == expected_output


def test_character_text_splitter_longer_words() -> None:
    """Test splitting by characters when splits not found easily."""
    text = "foo bar baz 123"
    splitter = CharacterTextSplitter(separator=" ", chunk_size=1, chunk_overlap=1)
    output = splitter.split_text(text)
    expected_output = ["foo", "bar", "baz", "123"]
    assert output == expected_output


def test_character_text_splitting_args() -> None:
    """Test invalid arguments."""
    with pytest.raises(ValueError):
        CharacterTextSplitter(chunk_size=2, chunk_overlap=4)


def test_merge_splits() -> None:
    """Test merging splits with a given separator."""
    splitter = CharacterTextSplitter(separator=" ", chunk_size=9, chunk_overlap=2)
    splits = ["foo", "bar", "baz"]
    expected_output = ["foo bar", "baz"]
    output = splitter._merge_splits(splits, separator=" ")
    assert output == expected_output


def test_create_documents() -> None:
    """Test create documents method."""
    texts = ["foo bar", "baz"]
    splitter = CharacterTextSplitter(separator=" ", chunk_size=3, chunk_overlap=0)
    docs = splitter.create_documents(texts)
    expected_docs = [
        Document(page_content="foo"),
        Document(page_content="bar"),
        Document(page_content="baz"),
    ]
    assert docs == expected_docs


def test_create_documents_with_metadata() -> None:
    """Test create documents with metadata method."""
    texts = ["foo bar", "baz"]
    splitter = CharacterTextSplitter(separator=" ", chunk_size=3, chunk_overlap=0)
    docs = splitter.create_documents(texts, [{"source": "1"}, {"source": "2"}])
    expected_docs = [
        Document(page_content="foo", metadata={"source": "1"}),
        Document(page_content="bar", metadata={"source": "1"}),
        Document(page_content="baz", metadata={"source": "2"}),
    ]
    assert docs == expected_docs


def test_metadata_not_shallow() -> None:
    """Test that metadatas are not shallow."""
    texts = ["foo bar"]
    splitter = CharacterTextSplitter(separator=" ", chunk_size=3, chunk_overlap=0)
    docs = splitter.create_documents(texts, [{"source": "1"}])
    expected_docs = [
        Document(page_content="foo", metadata={"source": "1"}),
        Document(page_content="bar", metadata={"source": "1"}),
    ]
    assert docs == expected_docs
    docs[0].metadata["foo"] = 1
    assert docs[0].metadata == {"source": "1", "foo": 1}
    assert docs[1].metadata == {"source": "1"}


def test_iterative_text_splitter() -> None:
    """Test iterative text splitter."""
    text = """Hi.\n\nI'm Harrison.\n\nHow? Are? You?\nOkay then f f f f.
This is a weird text to write, but gotta test the splittingggg some how.

Bye!\n\n-H."""
    splitter = RecursiveCharacterTextSplitter(chunk_size=10, chunk_overlap=1)
    output = splitter.split_text(text)
    expected_output = [
        "Hi.",
        "I'm",
        "Harrison.",
        "How? Are?",
        "You?",
        "Okay then",
        "f f f f.",
        "This is a",
        "a weird",
        "text to",
        "write, but",
        "gotta test",
        "the",
        "splittingg",
        "ggg",
        "some how.",
        "Bye!\n\n-H.",
    ]
    assert output == expected_output