refactor: test organisation and service test (#27991)

* refactor: test organisation

# Conflicts:
#	mobile/test/unit/utils/editor_test.dart

* regroup hash_service_test

---------

Co-authored-by: shenlong-tanwen <139912620+shalong-tanwen@users.noreply.github.com>

mobile/test/utils.dart

@@ -0,0 +1,10 @@
+import 'package:uuid/uuid.dart';
+
+class TestUtils {
+  static String uuid([String? id]) => id ?? const Uuid().v4();
+
+  static DateTime date([DateTime? date]) => date ?? DateTime.now();
+  static DateTime now() => DateTime.now();
+  static DateTime yesterday() => DateTime.now().subtract(const Duration(days: 1));
+  static DateTime tomorrow() => DateTime.now().add(const Duration(days: 1));
+}