[V1] Make v1 more testable (#9888)

Signed-off-by: Joe Runde <Joseph.Runde@ibm.com>

tests/entrypoints/llm/test_prompt_validation.py

@@ -3,12 +3,21 @@ import pytest
 from vllm import LLM
 
 
+@pytest.fixture(autouse=True)
+def v1(run_with_both_engines):
+    # Simple autouse wrapper to run both engines for each test
+    # This can be promoted up to conftest.py to run for every
+    # test in a package
+    pass
+
+
 def test_empty_prompt():
     llm = LLM(model="gpt2", enforce_eager=True)
     with pytest.raises(ValueError, match='Prompt cannot be empty'):
         llm.generate([""])
 
 
+@pytest.mark.skip_v1
 def test_out_of_vocab_token():
     llm = LLM(model="gpt2", enforce_eager=True)
     with pytest.raises(ValueError, match='out of vocabulary'):