[Bug] Fix Failure in /v1/chat/completions/render for Multimodal Requests (https://github.com/vllm-project/vllm/issues/35665) (#35684)

tests/entrypoints/openai/cpu/test_render_multimodal.py

@@ -0,0 +1,155 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+
+"""Multimodal tests for the /render endpoints that expose prompt preprocessing."""
+
+import httpx
+import pytest
+import pytest_asyncio
+
+from tests.utils import RemoteOpenAIServer
+from vllm.multimodal.utils import encode_image_url
+
+VISION_MODEL_NAME = "Qwen/Qwen3-VL-2B-Instruct"
+
+
+@pytest.fixture(scope="module")
+def vision_server():
+    """Vision-capable server used for multimodal /render tests."""
+
+    args = [
+        "--enforce-eager",
+        "--max-model-len",
+        "100",
+        "--max-num-seqs",
+        "1",
+        "--limit-mm-per-prompt.image",
+        "1",
+        "--limit-mm-per-prompt.video",
+        "0",
+    ]
+
+    env_overrides: dict[str, str] = {}
+
+    with RemoteOpenAIServer(
+        VISION_MODEL_NAME,
+        args,
+        env_dict=env_overrides,
+    ) as remote_server:
+        yield remote_server
+
+
+@pytest_asyncio.fixture
+async def vision_client(vision_server):
+    async with httpx.AsyncClient(
+        base_url=vision_server.url_for(""), timeout=60.0
+    ) as http_client:
+        yield http_client
+
+
+@pytest.mark.asyncio
+async def test_chat_completion_render_with_base64_image_url(
+    vision_client,
+    local_asset_server,
+):
+    """Render a multimodal chat request and verify tokens are returned."""
+
+    image = local_asset_server.get_image_asset("RGBA_comp.png")
+    data_url = encode_image_url(image, format="PNG")
+
+    assert data_url.startswith("data:image/")
+    assert ";base64," in data_url
+
+    response = await vision_client.post(
+        "/v1/chat/completions/render",
+        json={
+            "model": VISION_MODEL_NAME,
+            "messages": [
+                {
+                    "role": "user",
+                    "content": [
+                        {"type": "image_url", "image_url": {"url": data_url}},
+                        {"type": "text", "text": "What's in this image?"},
+                    ],
+                }
+            ],
+        },
+    )
+
+    assert response.status_code == 200
+
+    data = response.json()
+    assert isinstance(data, dict)
+    assert "token_ids" in data
+    assert isinstance(data["token_ids"], list)
+    assert len(data["token_ids"]) > 0
+
+    # Verify multimodal features are populated
+    assert "features" in data
+    features = data["features"]
+    assert features is not None
+
+    # mm_hashes: should have an "image" key with a list of hash strings
+    assert "mm_hashes" in features
+    assert "image" in features["mm_hashes"]
+    image_hashes = features["mm_hashes"]["image"]
+    assert isinstance(image_hashes, list)
+    assert len(image_hashes) > 0
+    assert all(isinstance(h, str) for h in image_hashes)
+
+    # mm_placeholders: should have an "image" key with offset/length dicts
+    assert "mm_placeholders" in features
+    assert "image" in features["mm_placeholders"]
+    image_placeholders = features["mm_placeholders"]["image"]
+    assert isinstance(image_placeholders, list)
+    assert len(image_placeholders) > 0
+    for p in image_placeholders:
+        assert "offset" in p
+        assert "length" in p
+        assert isinstance(p["offset"], int)
+        assert isinstance(p["length"], int)
+        assert p["length"] > 0
+
+
+@pytest.mark.asyncio
+async def test_tokenize_matches_render_for_multimodal_input(
+    vision_client,
+    local_asset_server,
+):
+    """`/tokenize` should match `/v1/chat/completions/render` token output."""
+
+    image = local_asset_server.get_image_asset("RGBA_comp.png")
+    data_url = encode_image_url(image, format="PNG")
+
+    messages = [
+        {
+            "role": "user",
+            "content": [
+                {"type": "image_url", "image_url": {"url": data_url}},
+                {"type": "text", "text": "What's in this image?"},
+            ],
+        }
+    ]
+
+    render_response = await vision_client.post(
+        "/v1/chat/completions/render",
+        json={
+            "model": VISION_MODEL_NAME,
+            "messages": messages,
+        },
+    )
+    assert render_response.status_code == 200
+    render_data = render_response.json()
+
+    tokenize_response = await vision_client.post(
+        "/tokenize",
+        json={
+            "model": VISION_MODEL_NAME,
+            "messages": messages,
+        },
+    )
+    assert tokenize_response.status_code == 200
+    tokenize_data = tokenize_response.json()
+
+    assert tokenize_data["tokens"] == render_data["token_ids"]
+    assert tokenize_data["count"] == len(render_data["token_ids"])