[Spec Decode] Introduce DraftModelRunner (#5799)

tests/spec_decode/test_multi_step_worker.py

@@ -7,6 +7,7 @@ import torch
 
 from vllm.model_executor.utils import set_random_seed
 from vllm.sequence import ExecuteModelRequest, Logprob, SamplerOutput
+from vllm.spec_decode.draft_model_runner import TP1DraftModelRunner
 from vllm.spec_decode.multi_step_worker import MultiStepWorker
 from vllm.spec_decode.top1_proposer import Top1Proposer
 from vllm.worker.worker import Worker
@@ -85,6 +86,7 @@ def test_same_output_for_single_step():
         block_size,
         num_gpu_blocks,
         seed,
+        model_runner_cls=TP1DraftModelRunner,
     )
     worker = create_worker(
         Worker,
@@ -168,6 +170,7 @@ def test_same_output_for_multi_step():
         block_size,
         num_gpu_blocks,
         seed,
+        model_runner_cls=TP1DraftModelRunner,
     )
 
     worker = create_worker(