Save grain trace data to HDF5 format

tests/conftest.py

@@ -1,4 +1,5 @@
 """Fixtures for testing."""
+
 import importlib.resources as pkg_resources
 from pathlib import Path
 
@@ -346,6 +347,12 @@ def load_scan_dummy() -> LoadScans:
     return LoadScans(img_paths="dummy", channel="dummy")
 
 
+@pytest.fixture()
+def load_scan_topostats_test_file(tmp_path: Path, loading_config: dict) -> LoadScans:
+    """Instantiate a LoadScans object for a temporarily saved test .topostats file."""
+    return LoadScans([tmp_path / "topostats_file_test.topostats"], **loading_config)
+
+
 @pytest.fixture()
 def load_scan(loading_config: dict) -> LoadScans:
     """Instantiate a LoadScans object from a small .topostats image file."""