Preserve validation manifests in failure sampling

backend/tests/test_failure_driven_yolo_sampling.py

@@ -11,6 +11,17 @@ MODULE = importlib.util.module_from_spec(SPEC)
 SPEC.loader.exec_module(MODULE)
 
 
+def test_dataset_validation_source_preserves_manifest_path(tmp_path: Path):
+    source = tmp_path / "dataset.yaml"
+    source.write_text(
+        "path: /data/source\ntrain: /data/source/train.txt\n"
+        "val: /data/source/internal-val.txt\nnames:\n  0: building\n",
+        encoding="utf-8",
+    )
+
+    assert MODULE.dataset_validation_source(source) == "/data/source/internal-val.txt"
+
+
 def test_sampling_repeats_only_failed_region_train_tiles() -> None:
     manifest = {
         "samples": [