add source library test

Author: nvaytet

tests/facilities/source_library_test.py

@@ -0,0 +1,38 @@
+# SPDX-License-Identifier: BSD-3-Clause
+# Copyright (c) 2026 Scipp contributors (https://github.com/scipp)
+
+import hashlib
+from pathlib import Path
+
+import pooch
+
+from tof.facilities import _BASE_URLS, _source_library
+
+
+def sha256(p: Path) -> str:
+    h = hashlib.sha256()
+    with p.open("rb") as f:
+        for chunk in iter(lambda: f.read(1024 * 1024), b""):
+            h.update(chunk)
+    return h.hexdigest()
+
+
+def test_source_library_files_identical_on_public_and_github(tmp_path: Path) -> None:
+    registry = {f["path"]: f["hash"] for f in _source_library.values()}
+
+    public = pooch.create(
+        path=tmp_path / "cache_public", base_url=_BASE_URLS[0], registry=registry
+    )
+
+    gh = pooch.create(
+        path=tmp_path / "cache_github", base_url=_BASE_URLS[1], registry=registry
+    )
+
+    for name, entry in _source_library.items():
+        rel = entry["path"]
+
+        p_gh = Path(gh.fetch(rel))
+        p_public = Path(public.fetch(rel))
+
+        # registry already verifies md5, but we compare content across hosts:
+        assert sha256(p_gh) == sha256(p_public), f"Mismatch for {name} ({rel})"