Recursive url loader w/ test (#8813)

Description: Due to some issue on the test, this is a separate PR with
the test for #8502

Tag maintainer: @rlancemartin

---------

Co-authored-by: Lance Martin <lance@langchain.dev>
Co-authored-by: Bagatur <baskaryan@gmail.com>

libs/langchain/tests/integration_tests/document_loaders/test_recursive_url_loader.py

@@ -0,0 +1,30 @@
+from langchain.document_loaders.recursive_url_loader import RecursiveUrlLoader
+
+
+def test_async_recursive_url_loader() -> None:
+    url = "https://docs.python.org/3.9/"
+    loader = RecursiveUrlLoader(
+        url=url, extractor=lambda _: "placeholder", use_async=True, max_depth=1
+    )
+    docs = loader.load()
+    assert len(docs) == 24
+    assert docs[0].page_content == "placeholder"
+
+
+def test_sync_recursive_url_loader() -> None:
+    url = "https://docs.python.org/3.9/"
+    loader = RecursiveUrlLoader(
+        url=url, extractor=lambda _: "placeholder", use_async=False, max_depth=1
+    )
+    docs = loader.load()
+    assert len(docs) == 24
+    assert docs[0].page_content == "placeholder"
+
+
+def test_loading_invalid_url() -> None:
+    url = "https://this.url.is.invalid/this/is/a/test"
+    loader = RecursiveUrlLoader(
+        url=url, max_depth=1, extractor=lambda _: "placeholder", use_async=False
+    )
+    docs = loader.load()
+    assert len(docs) == 0