[Bugfix] Limit Qwen-Image-Edit-2511 input image count (#2840)

Signed-off-by: david6666666 <530634352@qq.com>
Co-authored-by: Gao Han <hgaoaf@connect.ust.hk>

tests/diffusion/models/qwen_image/test_qwen_image_edit_plus.py

@@ -0,0 +1,38 @@
+# SPDX-License-Identifier: Apache-2.0
+
+import json
+from pathlib import Path
+from types import SimpleNamespace
+
+import numpy as np
+import pytest
+from PIL import Image
+
+from vllm_omni.diffusion.models.qwen_image.pipeline_qwen_image_edit_plus import (
+    get_qwen_image_edit_plus_pre_process_func,
+)
+
+pytestmark = [pytest.mark.core_model, pytest.mark.diffusion, pytest.mark.cpu]
+
+
+def test_qwen_image_edit_plus_rejects_too_many_input_images(tmp_path: Path):
+    vae_dir = tmp_path / "vae"
+    vae_dir.mkdir()
+    # Keep the mock config intentionally minimal: this test only needs the
+    # fields touched during pre-process initialization.
+    (vae_dir / "config.json").write_text(json.dumps({"z_dim": 16}))
+
+    pre_process = get_qwen_image_edit_plus_pre_process_func(SimpleNamespace(model=str(tmp_path)))
+    image = Image.fromarray(np.zeros((32, 32, 3), dtype=np.uint8))
+    request = SimpleNamespace(
+        prompts=[
+            {
+                "prompt": "combine",
+                "multi_modal_data": {"image": [image, image, image, image, image]},
+            }
+        ],
+        sampling_params=SimpleNamespace(height=None, width=None),
+    )
+
+    with pytest.raises(ValueError, match=r"At most 4 images are supported by this model"):
+        pre_process(request)