[Test] Only Run MLA model when user explicitly set for batch invariance (#37719)

Signed-off-by: yewentao256 <zhyanwentao@126.com>

tests/v1/determinism/utils.py

@@ -7,6 +7,10 @@ import pytest
 import torch
 
 from vllm.platforms import current_platform
+from vllm.transformers_utils.config import get_config
+from vllm.transformers_utils.model_arch_config_convertor import (
+    ModelArchConfigConvertorBase,
+)
 from vllm.v1.attention.backends.fa_utils import flash_attn_supports_mla
 
 skip_unsupported = pytest.mark.skipif(
@@ -16,10 +20,12 @@ skip_unsupported = pytest.mark.skipif(
     reason="Requires CUDA and >= Ampere (SM80)",
 )
 
+DEFAULT_MODEL = "Qwen/Qwen3-1.7B"
+TEST_MODEL = os.getenv("VLLM_TEST_MODEL", DEFAULT_MODEL)
+
 BACKENDS: list[str] = [
     "FLASH_ATTN",
     "TRITON_ATTN",
-    "TRITON_MLA",
 ]
 
 # FlashInfer temporarily disabled due to invariant CTA sizes.
@@ -27,19 +33,13 @@ BACKENDS: list[str] = [
 # if has_flashinfer():
 #     BACKENDS.append("FLASHINFER")
 
-if flash_attn_supports_mla():
-    BACKENDS.append("FLASH_ATTN_MLA")
-
-DEFAULT_MODEL = "Qwen/Qwen3-1.7B"
-MLA_MODEL = "deepseek-ai/DeepSeek-V2-Lite-Chat"
-
-
-def resolve_model_name(backend: str) -> str:
-    """Resolve the model name for the given backend."""
-    model = os.getenv("VLLM_TEST_MODEL", DEFAULT_MODEL)
-    if backend.endswith("MLA") and model == DEFAULT_MODEL:
-        return MLA_MODEL
-    return model
+# only run MLA backends when the requested test model is itself an MLA model.
+if os.getenv("VLLM_TEST_MODEL"):
+    config = get_config(TEST_MODEL, trust_remote_code=False)
+    if ModelArchConfigConvertorBase(config, config.get_text_config()).is_deepseek_mla():
+        BACKENDS = ["TRITON_MLA"]
+        if flash_attn_supports_mla():
+            BACKENDS.append("FLASH_ATTN_MLA")
 
 
 def _random_prompt(min_words: int = 1024, max_words: int = 1024 * 2) -> str: