[Bugfix][CPU] Fix basic unit tests failing in CPU platforms (#34677)

Signed-off-by: Yanwen Lin <lyw1124278064@gmail.com>
Co-authored-by: Harry Mellor <19981378+hmellor@users.noreply.github.com>

tests/test_config.py

@@ -926,9 +926,14 @@ def test_vllm_config_defaults(model_id, compiliation_config, optimization_level)
     # Verify other compilation_config defaults
     compilation_config_dict = default_config["compilation_config"]
     for k, v in compilation_config_dict.items():
-        if k != "pass_config":
+        if k == "pass_config":
+            continue
         actual = getattr(vllm_config.compilation_config, k)
         expected = v(vllm_config) if callable(v) else v
+        # On platforms without static graph support, __post_init__ forces
+        # cudagraph_mode to NONE; expect that instead of the level default.
+        if k == "cudagraph_mode" and not current_platform.support_static_graph_mode():
+            expected = CUDAGraphMode.NONE
         assert actual == expected, (
             f"compilation_config.{k}: expected {expected}, got {actual}"
         )
@@ -969,6 +974,10 @@ def test_vllm_config_callable_defaults():
     assert enable_if_sequential(config_quantized) is True
 
 
+@pytest.mark.skipif(
+    not current_platform.support_static_graph_mode(),
+    reason="Explicit overrides may be force-overwritten without static graph support.",
+)
 def test_vllm_config_explicit_overrides():
     """Test that explicit property overrides work correctly with callable defaults.