bedrock: add unit test for retriever (#21485)

This was implemented in
https://github.com/langchain-ai/langchain/pull/21349 but dropped before
merge.

libs/community/tests/unit_tests/retrievers/test_bedrock.py

@@ -0,0 +1,68 @@
+from typing import List
+from unittest.mock import MagicMock
+
+import pytest
+from langchain_core.documents import Document
+
+from langchain_community.retrievers import AmazonKnowledgeBasesRetriever
+
+
+@pytest.fixture
+def mock_client() -> MagicMock:
+    return MagicMock()
+
+
+@pytest.fixture
+def mock_retriever_config() -> dict:
+    return {"vectorSearchConfiguration": {"numberOfResults": 4}}
+
+
+@pytest.fixture
+def amazon_retriever(
+    mock_client: MagicMock, mock_retriever_config: dict
+) -> AmazonKnowledgeBasesRetriever:
+    return AmazonKnowledgeBasesRetriever(
+        knowledge_base_id="test_kb_id",
+        retrieval_config=mock_retriever_config,
+        client=mock_client,
+    )
+
+
+def test_create_client(amazon_retriever: AmazonKnowledgeBasesRetriever) -> None:
+    with pytest.raises(ImportError):
+        amazon_retriever.create_client({})
+
+
+def test_get_relevant_documents(
+    amazon_retriever: AmazonKnowledgeBasesRetriever, mock_client: MagicMock
+) -> None:
+    query: str = "test query"
+    mock_client.retrieve.return_value = {
+        "retrievalResults": [
+            {"content": {"text": "result1"}, "metadata": {"key": "value1"}},
+            {
+                "content": {"text": "result2"},
+                "metadata": {"key": "value2"},
+                "score": 1,
+                "location": "testLocation",
+            },
+            {"content": {"text": "result3"}},
+        ]
+    }
+    documents: List[Document] = amazon_retriever._get_relevant_documents(
+        query,
+        run_manager=None,  # type: ignore
+    )
+
+    assert len(documents) == 3
+    assert isinstance(documents[0], Document)
+    assert documents[0].page_content == "result1"
+    assert documents[0].metadata == {"score": 0, "source_metadata": {"key": "value1"}}
+    assert documents[1].page_content == "result2"
+    assert documents[1].metadata == {
+        "score": 1,
+        "source_metadata": {"key": "value2"},
+        "location": "testLocation",
+    }
+    assert documents[2].page_content == "result3"
+    assert documents[2].metadata == {"score": 0}