[Tests] Tiny Diffusion Model Pattern (#4524)

Signed-off-by: Alex Brooks <albrooks@redhat.com>

tests/model_tests/diffusion/utils.py

@@ -0,0 +1,33 @@
+"""
+Utilities for resolving real models to their tiny model equivalents.
+"""
+
+import logging
+
+from tests.model_tests.diffusion.model_settings import DIFFUSION_TEST_SETTINGS
+from vllm_omni.diffusion.data import resolve_model_class_name
+
+logger = logging.getLogger(__name__)
+
+
+def resolve_tiny_model_path(model: str) -> str:
+    """Given a real model name/path, resolve it to a tiny model path.
+
+    Raises ValueError if the pipeline class cannot be determined (invalid
+    model). Returns the original model path if no tiny builder exists yet."""
+    pipeline_class = resolve_model_class_name(model)
+    if pipeline_class is None:
+        raise ValueError(
+            f"Cannot resolve pipeline class for model: {model}. The model path may be invalid or its config unreadable."
+        )
+
+    test_opts = DIFFUSION_TEST_SETTINGS.get(pipeline_class)
+    if test_opts is None:
+        logger.warning(
+            "No tiny model builder for pipeline %s (model: %s). Using original model.",
+            pipeline_class,
+            model,
+        )
+        return model
+
+    return test_opts.builder()