Implements NLTK and Spacy-based TextSplitters (#103)

This PR is for Issue #88 

- [x] `make format`
- [x] `make lint`
- [x] `make tests`

tests/integration_tests/test_nlp_text_splitters.py

@@ -0,0 +1,38 @@
+"""
+Test text splitting functionality using NLTK and Spacy based sentence splitters.
+"""
+import pytest
+
+from langchain.text_splitter import NLTKTextSplitter, SpacyTextSplitter
+
+
+def test_nltk_text_splitting_args() -> None:
+    """Test invalid arguments."""
+    with pytest.raises(ValueError):
+        NLTKTextSplitter(chunk_size=2, chunk_overlap=4)
+
+
+def test_spacy_text_splitting_args() -> None:
+    """Test invalid arguments."""
+    with pytest.raises(ValueError):
+        SpacyTextSplitter(chunk_size=2, chunk_overlap=4)
+
+
+def test_nltk_text_splitter() -> None:
+    """Test splitting by sentence using NLTK."""
+    text = "This is sentence one. And this is sentence two."
+    separator = "|||"
+    splitter = NLTKTextSplitter(separator=separator)
+    output = splitter.split_text(text)
+    expected_output = [f"This is sentence one.{separator}And this is sentence two."]
+    assert output == expected_output
+
+
+def test_spacy_text_splitter() -> None:
+    """Test splitting by sentence using Spacy."""
+    text = "This is sentence one. And this is sentence two."
+    separator = "|||"
+    splitter = SpacyTextSplitter(separator=separator)
+    output = splitter.split_text(text)
+    expected_output = [f"This is sentence one.{separator}And this is sentence two."]
+    assert output == expected_output