[custom_op][vllm-plugin] update custom_op class to use op_registry (#19164)

Signed-off-by: Chendi.Xue <chendi.xue@intel.com>

tests/plugins_tests/test_platform_plugins.py

@@ -5,6 +5,7 @@ import pytest
 import torch
 
 from vllm.attention.selector import get_attn_backend
+from vllm.plugins import load_general_plugins
 from vllm.utils import STR_BACKEND_ENV_VAR, STR_INVALID_VAL
 
 
@@ -32,3 +33,16 @@ def test_oot_attention_backend(monkeypatch: pytest.MonkeyPatch):
         m.setenv(STR_BACKEND_ENV_VAR, STR_INVALID_VAL)
         backend = get_attn_backend(16, torch.float16, "auto", 16, False)
         assert backend.get_name() == "Dummy_Backend"
+
+
+def test_oot_custom_op(monkeypatch: pytest.MonkeyPatch):
+    # simulate workload by running an example
+    load_general_plugins()
+    from vllm.model_executor.layers.rotary_embedding import RotaryEmbedding
+    layer = RotaryEmbedding(16, 16, 16, 16, True, torch.float16)
+    assert layer.__class__.__name__ == "DummyRotaryEmbedding", (
+        f"Expected DummyRotaryEmbedding, got {layer.__class__.__name__}, "
+        "possibly because the custom op is not registered correctly.")
+    assert hasattr(layer, "addition_config"), (
+        "Expected DummyRotaryEmbedding to have an 'addition_config' attribute, "
+        "which is set by the custom op.")