test: added unit tests for rag (#298)

* test: added unit tests for rag

* reformate the code

tests/unit/rag/test_retriever.py

@@ -0,0 +1,72 @@
+# Copyright (c) 2025 Bytedance Ltd. and/or its affiliates
+# SPDX-License-Identifier: MIT
+
+import pytest
+from src.rag.retriever import Chunk, Document, Resource, Retriever
+
+
+def test_chunk_init():
+    chunk = Chunk(content="test content", similarity=0.9)
+    assert chunk.content == "test content"
+    assert chunk.similarity == 0.9
+
+
+def test_document_init_and_to_dict():
+    chunk1 = Chunk(content="chunk1", similarity=0.8)
+    chunk2 = Chunk(content="chunk2", similarity=0.7)
+    doc = Document(
+        id="doc1", url="http://example.com", title="Title", chunks=[chunk1, chunk2]
+    )
+    assert doc.id == "doc1"
+    assert doc.url == "http://example.com"
+    assert doc.title == "Title"
+    assert doc.chunks == [chunk1, chunk2]
+    d = doc.to_dict()
+    assert d["id"] == "doc1"
+    assert d["content"] == "chunk1\n\nchunk2"
+    assert d["url"] == "http://example.com"
+    assert d["title"] == "Title"
+
+
+def test_document_to_dict_optional_fields():
+    chunk = Chunk(content="only chunk", similarity=1.0)
+    doc = Document(id="doc2", chunks=[chunk])
+    d = doc.to_dict()
+    assert d["id"] == "doc2"
+    assert d["content"] == "only chunk"
+    assert "url" not in d
+    assert "title" not in d
+
+
+def test_resource_model():
+    resource = Resource(uri="uri1", title="Resource Title")
+    assert resource.uri == "uri1"
+    assert resource.title == "Resource Title"
+    assert resource.description == ""
+
+
+def test_resource_model_with_description():
+    resource = Resource(uri="uri2", title="Resource2", description="desc")
+    assert resource.description == "desc"
+
+
+def test_retriever_abstract_methods():
+    class DummyRetriever(Retriever):
+        def list_resources(self, query=None):
+            return [Resource(uri="uri", title="title")]
+
+        def query_relevant_documents(self, query, resources=[]):
+            return [Document(id="id", chunks=[])]
+
+    retriever = DummyRetriever()
+    resources = retriever.list_resources()
+    assert isinstance(resources, list)
+    assert isinstance(resources[0], Resource)
+    docs = retriever.query_relevant_documents("query", resources)
+    assert isinstance(docs, list)
+    assert isinstance(docs[0], Document)
+
+
+def test_retriever_cannot_instantiate():
+    with pytest.raises(TypeError):
+        Retriever()