Add rerank semantic validation tests

tests/integration/inference/test_rerank.py

@@ -52,6 +52,28 @@ def _validate_rerank_response(response: RerankResponse, items: list) -> None:
         last_score = d.relevance_score
 
 
+def _validate_semantic_ranking(response: RerankResponse, items: list, expected_first_item: str) -> None:
+    """
+    Validate that the expected most relevant item ranks first.
+
+    Args:
+        response: The RerankResponse to validate
+        items: The original items list that was ranked
+        expected_first_item: The expected first item in the ranking
+
+    Raises:
+        AssertionError: If any validation fails
+    """
+    if not response.data:
+        raise AssertionError("No ranking data returned in response")
+
+    actual_first_index = response.data[0].index
+    actual_first_item = items[actual_first_index]
+    assert actual_first_item == expected_first_item, (
+        f"Expected '{expected_first_item}' to rank first, but '{actual_first_item}' ranked first instead."
+    )
+
+
 @pytest.mark.parametrize(
     "query,items",
     [
@@ -145,3 +167,47 @@ def test_rerank_max_results_larger_than_items(client_with_models, rerank_model_i
 
     assert isinstance(response, RerankResponse)
     assert len(response.data) <= len(items)  # Should return at most len(items)
+
+
+@pytest.mark.parametrize(
+    "query,items,expected_first_item",
+    [
+        (
+            "What is a reranking model? ",
+            [
+                "A reranking model reranks a list of items based on the query. ",
+                "Machine learning algorithms learn patterns from data. ",
+                "Python is a programming language. ",
+            ],
+            "A reranking model reranks a list of items based on the query. ",
+        ),
+        (
+            "What is C++?",
+            [
+                "Learning new things is interesting. ",
+                "C++ is a programming language. ",
+                "Books provide knowledge and entertainment. ",
+            ],
+            "C++ is a programming language. ",
+        ),
+        (
+            "What are good learning habits? ",
+            [
+                "Cooking pasta is a fun activity. ",
+                "Plants need water and sunlight. ",
+                "Good learning habits include reading daily and taking notes. ",
+            ],
+            "Good learning habits include reading daily and taking notes. ",
+        ),
+    ],
+)
+def test_rerank_semantic_correctness(
+    client_with_models, rerank_model_id, query, items, expected_first_item, inference_provider_type
+):
+    if inference_provider_type not in SUPPORTED_PROVIDERS:
+        pytest.xfail(f"{inference_provider_type} doesn't support rerank models yet.")
+
+    response = client_with_models.inference.rerank(model=rerank_model_id, query=query, items=items)
+
+    _validate_rerank_response(response, items)
+    _validate_semantic_ranking(response, items, expected_first_item)