[Speculative decoding 7/9] Speculative decoding end-to-end correctness tests. (#3951)

tests/spec_decode/utils.py

@@ -63,11 +63,14 @@ def create_execute_model_data(
 def mock_worker(cls=None,
                 vocab_size: int = 30_000,
                 max_model_len: int = 2048,
-                rank: int = 0) -> MagicMock:
+                rank: int = 0,
+                use_spec: bool = True) -> MagicMock:
     if cls is None:
         cls = Worker
 
-    worker = MagicMock(spec=cls)
+    spec = cls if use_spec else None
+
+    worker = MagicMock(spec=spec)
     worker.vocab_size = vocab_size
     worker.max_model_len = max_model_len
     worker.rank = rank