[Speculative decoding] CUDA graph support (vllm-project#4295)

Co-authored-by: Cade Daniel <edacih@gmail.com>

tests/spec_decode/e2e/test_multistep_correctness.py

@@ -611,3 +611,40 @@ def test_many_k(baseline_llm_generator, test_llm_generator, batch_size: int,
                                          batch_size,
                                          max_output_len=output_len,
                                          force_output_len=True)
+
+
+@pytest.mark.parametrize(
+    "common_llm_kwargs",
+    [{
+        # Required for spec decode.
+        "use_v2_block_manager": True,
+
+        # Verify equality when cuda graphs allowed.
+        "enforce_eager": False,
+        "model": "JackFram/llama-68m",
+    }])
+@pytest.mark.parametrize(
+    "per_test_common_llm_kwargs",
+    [
+        {
+            # Identical models.
+            "speculative_model": "JackFram/llama-68m",
+            "num_speculative_tokens": 5,
+        },
+    ])
+@pytest.mark.parametrize("baseline_llm_kwargs", [{}])
+@pytest.mark.parametrize("test_llm_kwargs", [{}])
+@pytest.mark.parametrize("batch_size", [8])
+@pytest.mark.parametrize("output_len", [32])
+@pytest.mark.parametrize("seed", [1])
+def test_spec_decode_cuda_graph(baseline_llm_generator, test_llm_generator,
+                                batch_size, output_len):
+    """Verify spec decode equality when cuda graphs are enabled.
+    """
+    run_greedy_equality_correctness_test(
+        baseline_llm_generator,
+        test_llm_generator,
+        batch_size,
+        max_output_len=output_len,
+        force_output_len=True,
+    )