migration test

tests/test_persistence.py

@@ -26,6 +26,25 @@ def test_save_load_roundtrip(tmp_path):
     assert loaded.version == content.SAVE_VERSION
 
 
+def test_migration(tmp_path):
+    cat = model.Save(
+        version=1,
+        cat=model.Cat(
+            "Fry",
+            {
+                "size": "tiny",
+                "color": "tuxedo",
+                "eyes": "blue",
+                "personality": "judges you silently",
+            },
+        ),
+    )
+    persistence.save(cat, tmp_path)
+    loaded = persistence.load("Fry", tmp_path)
+    assert loaded.cat.fullness
+    assert loaded.cat.last_updated
+
+
 def test_list_saves(tmp_path):
     open(tmp_path / "test.kitten", "w").close()
     open(tmp_path / "test2.kitten", "w").close()