closeAll static method
Saves and closes every open box (mostly useful in tests).
Implementation
static Future<void> closeAll() async {
final boxes = _openBoxes.values.toList();
final lazy = _openLazy.values.toList();
_openBoxes.clear();
_openLazy.clear();
await Future.wait([
...boxes.map((b) => b.close()),
...lazy.map((b) => b.close()),
]);
}