feat: DeviceListModifiedEvent now contains a delta

test/helpers_test.dart

@@ -0,0 +1,33 @@
+import 'package:omemo_dart/src/helpers.dart';
+import 'package:omemo_dart/src/omemo/queue.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group('List diff', () {
+    test('Empty list to full list', () {
+      final result = <int>[].diff([1, 2, 3, 4]);
+      expect(result.removed, isEmpty);
+      expect(
+        result.added.containsAll([1, 2, 3, 4]),
+        isTrue,
+      );
+      expect(result.added.length, 4);
+    });
+
+    test('Full list to empty list', () {
+      final result = [1, 2, 3, 4].diff([]);
+      expect(result.added, isEmpty);
+      expect(
+        result.removed.containsAll([1, 2, 3, 4]),
+        isTrue,
+      );
+      expect(result.removed.length, 4);
+    });
+
+    test('Full list to full list', () {
+      final result = [1, 2, 3, 4].diff([1, 2, 4, 5]);
+      expect(result.added, [5]);
+      expect(result.removed, [3]);
+    });
+  });
+}