test: add listeners tests

Author: juliansteenbakker

flutter_secure_storage/lib/flutter_secure_storage.dart

@@ -1,5 +1,7 @@
 library;
 
+import 'dart:collection';
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_secure_storage/test/test_flutter_secure_storage_platform.dart';
@@ -74,6 +76,11 @@ class FlutterSecureStorage {
   FlutterSecureStoragePlatform get _platform =>
       FlutterSecureStoragePlatform.instance;
 
+  /// Returns all listeners for testing purposes
+  @visibleForTesting
+  Map<String, List<ValueChanged<String?>>> get getListeners =>
+      UnmodifiableMapView(_listeners);
+
   /// Register [listener] for [key] with the value injected for the listener.
   /// The [listener] will still be called when you delete the [key] with the
   /// injected value as null. This listener will be added to the list of

flutter_secure_storage/test/flutter_secure_storage_test.dart

@@ -1,3 +1,4 @@
+import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_secure_storage/flutter_secure_storage.dart';
 import 'package:flutter_secure_storage/test/test_flutter_secure_storage_platform.dart';
@@ -560,4 +561,53 @@ void main() {
       expect(defaultOptions.toMap(), constructorOptions.toMap());
     });
   });
+
+  group('Listener Management Tests', () {
+    late ValueChanged<String?> listener1;
+    late ValueChanged<String?> listener2;
+
+    setUp(() {
+      storage.unregisterAllListeners();
+      listener1 = (value) => debugPrint('Listener 1: $value');
+      listener2 = (value) => debugPrint('Listener 2: $value');
+    });
+
+    test('Register listener adds correctly', () {
+      storage.registerListener(key: 'key1', listener: listener1);
+      expect(storage.getListeners['key1']?.contains(listener1), isTrue);
+    });
+
+    test('Register multiple listeners on same key', () {
+      storage
+        ..registerListener(key: 'key1', listener: listener1)
+        ..registerListener(key: 'key1', listener: listener2);
+      expect(storage.getListeners['key1']?.length, 2);
+      expect(storage.getListeners['key1'], containsAll([listener1, listener2]));
+    });
+
+    test('Unregister listener removes specific listener', () {
+      storage
+        ..registerListener(key: 'key1', listener: listener1)
+        ..registerListener(key: 'key1', listener: listener2)
+        ..unregisterListener(key: 'key1', listener: listener1);
+      expect(storage.getListeners['key1']?.contains(listener1), isFalse);
+      expect(storage.getListeners['key1']?.contains(listener2), isTrue);
+    });
+
+    test('Unregister all listeners for a key', () {
+      storage
+        ..registerListener(key: 'key1', listener: listener1)
+        ..registerListener(key: 'key1', listener: listener2)
+        ..unregisterAllListenersForKey(key: 'key1');
+      expect(storage.getListeners.containsKey('key1'), isFalse);
+    });
+
+    test('Unregister all listeners for all keys', () {
+      storage
+        ..registerListener(key: 'key1', listener: listener1)
+        ..registerListener(key: 'key2', listener: listener2)
+        ..unregisterAllListeners();
+      expect(storage.getListeners.isEmpty, isTrue);
+    });
+  });
 }