Add test for svm retriever (#7768)

# What
- This is to add unit test for svm retriever.

---------

Co-authored-by: Bagatur <baskaryan@gmail.com>

tests/unit_tests/retrievers/test_svm.py

@@ -0,0 +1,27 @@
+import pytest
+
+from langchain.embeddings import FakeEmbeddings
+from langchain.retrievers.svm import SVMRetriever
+from langchain.schema import Document
+
+
+class TestSVMRetriever:
+    @pytest.mark.requires("sklearn")
+    def test_from_texts(self) -> None:
+        input_texts = ["I have a pen.", "Do you have a pen?", "I have a bag."]
+        svm_retriever = SVMRetriever.from_texts(
+            texts=input_texts, embeddings=FakeEmbeddings(size=100)
+        )
+        assert len(svm_retriever.texts) == 3
+
+    @pytest.mark.requires("sklearn")
+    def test_from_documents(self) -> None:
+        input_docs = [
+            Document(page_content="I have a pen.", metadata={"foo": "bar"}),
+            Document(page_content="Do you have a pen?"),
+            Document(page_content="I have a bag."),
+        ]
+        svm_retriever = SVMRetriever.from_documents(
+            documents=input_docs, embeddings=FakeEmbeddings(size=100)
+        )
+        assert len(svm_retriever.texts) == 3