first test

tests/test_persistence.py

@@ -1 +1,9 @@
 from untitled import model, persistence
+
+
+def test_save_load_roundtrip(tmp_path):
+    original = model.Save(version=1, cat=model.Cat("Mittens"))
+    persistence.save(original)
+    loaded = persistence.load("Mittens")
+    assert loaded.cat.name == "Mittens"
+    assert loaded.version == 1