diff --git a/lib/src/json_cache.dart b/lib/src/json_cache.dart
index ffc66eb..42cf242 100644
--- a/lib/src/json_cache.dart
+++ b/lib/src/json_cache.dart
@@ -1,3 +1,5 @@
+import 'dart:collection';
+
 /// Represents cached data in json format.
 ///
 ///> Cache is a hardware or software component that stores data so that future
@@ -25,4 +27,9 @@ abstract class JsonCache {
   ///
   /// Returns `true` if there is cached data at [key]; `false` otherwise.
   Future<bool> contains(String key);
+
+  /// Lists all keys.
+  ///
+  /// Returns an **unmodifiable** list of cache keys without duplicates.
+  Future<UnmodifiableListView<String>> keys();
 }
diff --git a/lib/src/json_cache_exception.dart b/lib/src/json_cache_exception.dart
index fa3270d..ac6110c 100644
--- a/lib/src/json_cache_exception.dart
+++ b/lib/src/json_cache_exception.dart
@@ -11,7 +11,7 @@ class JsonCacheException<T extends Object> implements Exception {
 
   /// The original exception that indicated the failure of the caching
   /// operation.
-  final Exception? exception;
+  final Object? exception;
 
   /// Returns [extra] along with the original exception message.
   @override
diff --git a/lib/src/json_cache_fake.dart b/lib/src/json_cache_fake.dart
index 9cb4dd5..e293f5e 100644
--- a/lib/src/json_cache_fake.dart
+++ b/lib/src/json_cache_fake.dart
@@ -1,3 +1,5 @@
+import 'dart:collection';
+
 import 'package:json_cache/json_cache.dart';
 
 /// In-memory cache without synchronization.
@@ -50,4 +52,9 @@ class JsonCacheFake implements JsonCache {
   Future<bool> contains(String key) async {
     return _memory.containsKey(key);
   }
+
+  @override
+  Future<UnmodifiableListView<String>> keys() async {
+    return UnmodifiableListView(_memory.keys);
+  }
 }
diff --git a/lib/src/json_cache_flutter_secure_storage.dart b/lib/src/json_cache_flutter_secure_storage.dart
index 46e733c..3dad0fa 100644
--- a/lib/src/json_cache_flutter_secure_storage.dart
+++ b/lib/src/json_cache_flutter_secure_storage.dart
@@ -1,3 +1,4 @@
+import 'dart:collection';
 import 'dart:convert';
 
 import 'package:flutter_secure_storage/flutter_secure_storage.dart';
@@ -39,6 +40,11 @@ class JsonCacheFlutterSecureStorage implements JsonCache {
 
   @override
   Future<bool> contains(String key) async {
-    return _storage.containsKey(key: key);
+    return await _storage.containsKey(key: key);
+  }
+
+  @override
+  Future<UnmodifiableListView<String>> keys() async {
+    return UnmodifiableListView((await _storage.readAll()).keys);
   }
 }
diff --git a/lib/src/json_cache_hive.dart b/lib/src/json_cache_hive.dart
index 5911364..1b501fb 100644
--- a/lib/src/json_cache_hive.dart
+++ b/lib/src/json_cache_hive.dart
@@ -1,3 +1,4 @@
+import 'dart:collection';
 import 'dart:convert';
 
 import 'package:hive/hive.dart';
@@ -37,4 +38,9 @@ class JsonCacheHive implements JsonCache {
   Future<bool> contains(String key) async {
     return _box.containsKey(key);
   }
+
+  @override
+  Future<UnmodifiableListView<String>> keys() async {
+    return UnmodifiableListView(_box.keys.map((k) => k as String));
+  }
 }
diff --git a/lib/src/json_cache_hollow.dart b/lib/src/json_cache_hollow.dart
index f1fcfe8..5b96f69 100644
--- a/lib/src/json_cache_hollow.dart
+++ b/lib/src/json_cache_hollow.dart
@@ -1,3 +1,5 @@
+import 'dart:collection';
+
 import 'package:json_cache/json_cache.dart';
 
 /// Hollow (empty) [JsonCache] — It is intended to serve as a placeholder for
@@ -38,4 +40,9 @@ class JsonCacheHollow implements JsonCache {
   /// Always returns `false`.
   @override
   Future<bool> contains(String key) async => false;
+
+  /// An empty list of keys.
+  @override
+  Future<UnmodifiableListView<String>> keys() async =>
+      UnmodifiableListView(const []);
 }
diff --git a/lib/src/json_cache_local_storage.dart b/lib/src/json_cache_local_storage.dart
index 8b0325a..4d8e73e 100644
--- a/lib/src/json_cache_local_storage.dart
+++ b/lib/src/json_cache_local_storage.dart
@@ -1,3 +1,4 @@
+import 'dart:collection';
 import 'dart:convert';
 
 import 'package:json_cache/json_cache.dart';
@@ -44,4 +45,15 @@ final class JsonCacheLocalStorage implements JsonCache {
 
   @override
   Future<bool> contains(String key) async => _storage.getItem(key) != null;
+
+  @override
+  Future<UnmodifiableListView<String>> keys() async {
+    return UnmodifiableListView(
+      List.generate(
+        _storage.length,
+        (int i) => _storage.key(i)!,
+        growable: false,
+      ),
+    );
+  }
 }
diff --git a/lib/src/json_cache_mem.dart b/lib/src/json_cache_mem.dart
index 65be8a9..807cb9f 100644
--- a/lib/src/json_cache_mem.dart
+++ b/lib/src/json_cache_mem.dart
@@ -1,4 +1,5 @@
 import 'dart:async';
+import 'dart:collection';
 
 import 'package:json_cache/json_cache.dart';
 import 'package:mutex/mutex.dart';
@@ -93,8 +94,6 @@ class JsonCacheMem implements JsonCache {
   static final _shrMutex = ReadWriteMutex();
 
   /// Frees up storage space in both the level2 cache and in-memory cache.
-  ///
-  /// Throws [JsonCacheException] to indicate operation failure.
   @override
   Future<void> clear() async {
     await _mutex.protectWrite(() async {
@@ -105,8 +104,6 @@ class JsonCacheMem implements JsonCache {
 
   /// Updates the data located at [key] in both the _level 2_ cache and
   /// in-memory cache.
-  ///
-  /// Throws [JsonCacheException] to indicate operation failure.
   @override
   Future<void> refresh(String key, Map<String, dynamic> data) async {
     // ATTENTION: It is safer to copy the content of [data] before calling an
@@ -160,4 +157,11 @@ class JsonCacheMem implements JsonCache {
       return foundInMemory ? foundInMemory : await _level2.contains(key);
     });
   }
+
+  @override
+  Future<UnmodifiableListView<String>> keys() {
+    return _mutex.protectRead(() async {
+      return UnmodifiableListView(_memory.keys);
+    });
+  }
 }
diff --git a/lib/src/json_cache_safe_local_storage.dart b/lib/src/json_cache_safe_local_storage.dart
index 0ca86bd..b426e3f 100644
--- a/lib/src/json_cache_safe_local_storage.dart
+++ b/lib/src/json_cache_safe_local_storage.dart
@@ -1,5 +1,7 @@
 // ignore_for_file: avoid_dynamic_calls
 
+import 'dart:collection';
+
 import 'package:json_cache/json_cache.dart';
 import 'package:safe_local_storage/safe_local_storage.dart';
 
@@ -43,6 +45,14 @@ class JsonCacheSafeLocalStorage implements JsonCache {
     return (await _cachedData)[key] as Map<String, dynamic>?;
   }
 
+  @override
+  Future<UnmodifiableListView<String>> keys() async {
+    final data = await _cachedData;
+    return UnmodifiableListView(
+      data.keys.map((k) => k as String),
+    );
+  }
+
   /// Gets the cached data stored in the local storage file.
   Future<Map<dynamic, dynamic>> get _cachedData async {
     return await _localStorage.read() as Map<dynamic, dynamic>;
diff --git a/lib/src/json_cache_shared_preferences.dart b/lib/src/json_cache_shared_preferences.dart
index 9a58e5e..12749bc 100644
--- a/lib/src/json_cache_shared_preferences.dart
+++ b/lib/src/json_cache_shared_preferences.dart
@@ -1,3 +1,4 @@
+import 'dart:collection';
 import 'dart:convert';
 
 import 'package:json_cache/json_cache.dart';
@@ -47,4 +48,9 @@ class JsonCacheSharedPreferences implements JsonCache {
   Future<bool> contains(String key) async {
     return _sharedPreferences.containsKey(key);
   }
+
+  @override
+  Future<UnmodifiableListView<String>> keys() async {
+    return UnmodifiableListView(_sharedPreferences.getKeys());
+  }
 }
diff --git a/lib/src/json_cache_try.dart b/lib/src/json_cache_try.dart
index 820211e..0b59007 100644
--- a/lib/src/json_cache_try.dart
+++ b/lib/src/json_cache_try.dart
@@ -1,3 +1,5 @@
+import 'dart:collection';
+
 import 'package:json_cache/json_cache.dart';
 
 /// A [JsonCache] decorator that provides improved information about
@@ -103,4 +105,19 @@ class JsonCacheTry implements JsonCache {
       );
     }
   }
+
+  @override
+  Future<UnmodifiableListView<String>> keys() async {
+    try {
+      return await _wrapped.keys();
+    } on Exception catch (ex, st) {
+      Error.throwWithStackTrace(
+        JsonCacheException(
+          extra: "Error retreiving the cache keys.",
+          exception: ex,
+        ),
+        st,
+      );
+    }
+  }
 }
diff --git a/lib/src/json_cache_wrap.dart b/lib/src/json_cache_wrap.dart
index 7a25d78..5e39e04 100644
--- a/lib/src/json_cache_wrap.dart
+++ b/lib/src/json_cache_wrap.dart
@@ -1,3 +1,5 @@
+import 'dart:collection';
+
 import 'package:json_cache/json_cache.dart';
 
 /// Decorator Envelope of [JsonCache].
@@ -30,4 +32,8 @@ abstract class JsonCacheWrap implements JsonCache {
   /// Forwards to the [JsonCache.contains] of its wrapped instance.
   @override
   Future<bool> contains(String key) => _wrapped.contains(key);
+
+  /// Forwards to the [JsonCache.keys] of its wrapped instance.
+  @override
+  Future<UnmodifiableListView<String>> keys() => _wrapped.keys();
 }
diff --git a/test/flutter_secure_storage_mock.dart b/test/flutter_secure_storage_mock.dart
index ae0f976..34afcb1 100644
--- a/test/flutter_secure_storage_mock.dart
+++ b/test/flutter_secure_storage_mock.dart
@@ -90,9 +90,14 @@ class FlutterSecureStorageMock implements FlutterSecureStorage {
     WebOptions? webOptions,
     MacOsOptions? mOptions,
     WindowsOptions? wOptions,
-  }) {
-    // TODO: implement readAll
-    throw UnimplementedError();
+  }) async {
+    // final jsonObj = await _fakeCache.value(key);
+    final keys = await _fakeCache.keys();
+    final data = <String, String>{};
+    for (final key in keys) {
+      data[key] = json.encode(await _fakeCache.value(key));
+    }
+    return data;
   }
 
   @override
diff --git a/test/json_cache_fake_test.dart b/test/json_cache_fake_test.dart
index 49129ec..f263966 100644
--- a/test/json_cache_fake_test.dart
+++ b/test/json_cache_fake_test.dart
@@ -4,8 +4,8 @@ import 'package:json_cache/json_cache.dart';
 void main() {
   group('JsonCacheFake', () {
     const profKey = 'profile';
-    const profData = <String, dynamic>{'id': 1, 'name': 'John Due'};
     const prefKey = 'preferences';
+    const profData = <String, dynamic>{'id': 1, 'name': 'John Due'};
     const prefData = <String, dynamic>{
       'theme': 'dark',
       'notifications': {'enabled': true},
@@ -52,11 +52,6 @@ void main() {
     });
 
     test('contains', () async {
-      final profData = <String, dynamic>{'id': 1, 'name': 'John Due'};
-      final prefData = <String, dynamic>{
-        'theme': 'dark',
-        'notifications': {'enabled': true},
-      };
       final fake = JsonCacheFake();
       // update data
       await fake.refresh(profKey, profData);
@@ -70,6 +65,14 @@ void main() {
       expect(await fake.contains(prefKey), false);
       expect(await fake.contains('a key'), false);
     });
+    test('keys', () async {
+      final fake = JsonCacheFake();
+      // update data
+      await fake.refresh(profKey, profData);
+      await fake.refresh(prefKey, prefData);
+
+      expect(await fake.keys(), [profKey, prefKey]);
+    });
     group('remove', () {
       test('default ctor', () async {
         final JsonCacheFake fakeCache = JsonCacheFake();
diff --git a/test/json_cache_flutter_secure_storage_test.dart b/test/json_cache_flutter_secure_storage_test.dart
index 2c99c7c..b91dcc1 100644
--- a/test/json_cache_flutter_secure_storage_test.dart
+++ b/test/json_cache_flutter_secure_storage_test.dart
@@ -5,12 +5,17 @@ import 'flutter_secure_storage_mock.dart';
 
 void main() {
   group('JsonCacheFlutterSecureStorage', () {
+    const profKey = 'profile';
+    const prefKey = 'preferences';
+    const profData = <String, dynamic>{'id': 1, 'name': 'John Due'};
+    const prefData = <String, dynamic>{
+      'theme': 'dark',
+      'notifications': {'enabled': true},
+    };
     test('clear, value, refresh', () async {
       final secStorageMock = FlutterSecureStorageMock();
       final JsonCacheFlutterSecureStorage flutterSecureCache =
           JsonCacheFlutterSecureStorage(secStorageMock);
-      const profKey = 'profile';
-      const profData = <String, Object>{'id': 1, 'name': 'John Due'};
       await flutterSecureCache.refresh(profKey, profData);
       expect(secStorageMock.writeInvokations, 1);
 
@@ -27,13 +32,6 @@ void main() {
     });
 
     test('contains', () async {
-      const profKey = 'profile';
-      const prefKey = 'preferences';
-      final profData = <String, dynamic>{'id': 1, 'name': 'John Due'};
-      final prefData = <String, dynamic>{
-        'theme': 'dark',
-        'notifications': {'enabled': true},
-      };
       final secStorageMock = FlutterSecureStorageMock();
       final JsonCacheFlutterSecureStorage flutterSecureCache =
           JsonCacheFlutterSecureStorage(secStorageMock);
@@ -52,17 +50,20 @@ void main() {
       await flutterSecureCache.remove(prefKey);
       expect(await flutterSecureCache.contains(prefKey), false);
     });
+    test('keys', () async {
+      final secStorageMock = FlutterSecureStorageMock();
+      final JsonCacheFlutterSecureStorage flutterSecureCache =
+          JsonCacheFlutterSecureStorage(secStorageMock);
+      // update data
+      await flutterSecureCache.refresh(profKey, profData);
+      await flutterSecureCache.refresh(prefKey, prefData);
+
+      expect(await flutterSecureCache.keys(), [profKey, prefKey]);
+    });
     test('remove', () async {
       final secStorageMock = FlutterSecureStorageMock();
       final JsonCacheFlutterSecureStorage flutterSecureCache =
           JsonCacheFlutterSecureStorage(secStorageMock);
-      const profKey = 'profile';
-      const prefKey = 'preferences';
-      final profData = <String, Object>{'id': 1, 'name': 'John Due'};
-      final prefData = <String, Object>{
-        'theme': 'dark',
-        'notifications': {'enabled': true},
-      };
       await flutterSecureCache.refresh(profKey, profData);
       await flutterSecureCache.refresh(prefKey, prefData);
       expect(secStorageMock.writeInvokations, 2);
diff --git a/test/json_cache_hive_test.dart b/test/json_cache_hive_test.dart
index 0d74a6d..bbb0ad9 100644
--- a/test/json_cache_hive_test.dart
+++ b/test/json_cache_hive_test.dart
@@ -11,10 +11,15 @@ void main() {
     await tearDownTestHive();
   });
   group('JsonCacheHive', () {
+    const profKey = 'profile';
+    const prefKey = 'preferences';
+    const profData = <String, dynamic>{'id': 1, 'name': 'John Due'};
+    const prefData = <String, dynamic>{
+      'theme': 'dark',
+      'notifications': {'enabled': true},
+    };
     test('clear, value, refresh', () async {
       final box = await Hive.openBox<String>('test-clear-value-refresh');
-      const profKey = 'profile';
-      const profData = <String, Object>{'id': 1, 'name': 'John Due'};
       final JsonCacheHive hiveCache = JsonCacheHive(box);
       await hiveCache.refresh(profKey, profData);
       var prof = await hiveCache.value(profKey);
@@ -25,13 +30,6 @@ void main() {
     });
 
     test('contains', () async {
-      const profKey = 'profile';
-      const prefKey = 'preferences';
-      final profData = <String, dynamic>{'id': 1, 'name': 'John Due'};
-      final prefData = <String, dynamic>{
-        'theme': 'dark',
-        'notifications': {'enabled': true},
-      };
       final box = await Hive.openBox<String>('test-contains-method');
       final JsonCacheHive hiveCache = JsonCacheHive(box);
       // update data
@@ -49,14 +47,17 @@ void main() {
       await hiveCache.remove(prefKey);
       expect(await hiveCache.contains(prefKey), false);
     });
+
+    test('keys', () async {
+      final box = await Hive.openBox<String>('test-contains-method');
+      final JsonCacheHive hiveCache = JsonCacheHive(box);
+      // update data
+      await hiveCache.refresh(profKey, profData);
+      await hiveCache.refresh(prefKey, prefData);
+
+      expect(await hiveCache.keys(), [prefKey, profKey]);
+    });
     test('remove', () async {
-      const profKey = 'profile';
-      const prefKey = 'preferences';
-      final profData = <String, Object>{'id': 1, 'name': 'John Due'};
-      final prefData = <String, Object>{
-        'theme': 'dark',
-        'notifications': {'enabled': true},
-      };
       final box = await Hive.openBox<String>('test-remove');
       final hiveCache = JsonCacheHive(box);
       await hiveCache.refresh(profKey, profData);
diff --git a/test/json_cache_hollow_test.dart b/test/json_cache_hollow_test.dart
new file mode 100644
index 0000000..a54b1f2
--- /dev/null
+++ b/test/json_cache_hollow_test.dart
@@ -0,0 +1,68 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:json_cache/json_cache.dart';
+
+void main() {
+  group('JsonCacheHollow', () {
+    const profKey = 'profile';
+    const prefKey = 'preferences';
+    const profData = <String, dynamic>{'id': 1, 'name': 'John Due'};
+    const prefData = <String, dynamic>{
+      'theme': 'dark',
+      'notifications': {'enabled': true},
+    };
+
+    test('clear', () async {
+      const JsonCacheHollow hollowCache = JsonCacheHollow();
+      await hollowCache.refresh(profKey, profData);
+      await hollowCache.refresh(prefKey, prefData);
+      await hollowCache.clear();
+      final cachedProf = await hollowCache.value(profKey);
+      expect(cachedProf, isNull);
+      final cachedPref = await hollowCache.value(prefKey);
+      expect(cachedPref, isNull);
+    });
+
+    test('contains', () async {
+      const fake = JsonCacheHollow();
+      // update data
+      await fake.refresh(profKey, profData);
+      await fake.refresh(prefKey, prefData);
+
+      expect(await fake.contains(profKey), false);
+      expect(await fake.contains(prefKey), false);
+
+      await fake.remove(prefKey);
+      expect(await fake.contains(prefKey), false);
+      expect(await fake.contains('a key'), false);
+    });
+    test('keys', () async {
+      const fake = JsonCacheHollow();
+      await fake.refresh(profKey, profData);
+      await fake.refresh(prefKey, prefData);
+
+      expect(await fake.keys(), const []);
+    });
+    test('remove', () async {
+      const JsonCacheHollow hollowCache = JsonCacheHollow();
+      await hollowCache.refresh(profKey, profData);
+      await hollowCache.refresh(prefKey, prefData);
+      await hollowCache.remove(profKey);
+      final cachedProf = await hollowCache.value(profKey);
+      expect(cachedProf, isNull);
+      await hollowCache.remove(prefKey);
+      final cachedPref = await hollowCache.value(prefKey);
+      expect(cachedPref, isNull);
+    });
+    test('refresh and value', () async {
+      const JsonCacheHollow hollowCache = JsonCacheHollow();
+      await hollowCache.refresh(profKey, profData);
+      await hollowCache.refresh(prefKey, prefData);
+
+      final cachedProf = await hollowCache.value(profKey);
+      expect(cachedProf, isNull);
+
+      final cachedPref = await hollowCache.value(prefKey);
+      expect(cachedPref, isNull);
+    });
+  });
+}
diff --git a/test/json_cache_local_storage_test.dart b/test/json_cache_local_storage_test.dart
index 57c0412..b3eae78 100644
--- a/test/json_cache_local_storage_test.dart
+++ b/test/json_cache_local_storage_test.dart
@@ -5,9 +5,13 @@ import 'fake_local_storage.dart';
 
 void main() {
   group('JsonCacheLocalStorage', () {
+    const profKey = 'profile';
+    const profData = <String, Object>{'id': 1, 'name': 'John Due'};
+    const prefData = <String, dynamic>{
+      'theme': 'dark',
+      'notifications': {'enabled': true},
+    };
     test('clear, recover and refresh', () async {
-      const profKey = 'profile';
-      const profData = <String, Object>{'id': 1, 'name': 'John Due'};
       final JsonCacheLocalStorage jsonCache = _fakeInstance;
       await jsonCache.refresh(profKey, profData);
       var prof = await jsonCache.value(profKey);
@@ -18,13 +22,7 @@ void main() {
     });
 
     test('contains', () async {
-      const profKey = 'profile';
       const prefKey = 'preferences';
-      final profData = <String, dynamic>{'id': 1, 'name': 'John Due'};
-      final prefData = <String, dynamic>{
-        'theme': 'dark',
-        'notifications': {'enabled': true},
-      };
       final JsonCacheLocalStorage jsonCache = _fakeInstance;
       // update data
       await jsonCache.refresh(profKey, profData);
@@ -41,14 +39,18 @@ void main() {
       await jsonCache.remove(prefKey);
       expect(await jsonCache.contains(prefKey), false);
     });
+
+    test('keys', () async {
+      const prefKey = 'preferences';
+      final JsonCacheLocalStorage jsonCache = _fakeInstance;
+      // update data
+      await jsonCache.refresh(profKey, profData);
+      await jsonCache.refresh(prefKey, prefData);
+
+      expect(await jsonCache.keys(), [profKey, prefKey]);
+    });
     test('remove', () async {
-      const profKey = 'profile';
       const prefKey = 'preferences';
-      final profData = <String, Object>{'id': 1, 'name': 'John Due'};
-      final prefData = <String, Object>{
-        'theme': 'dark',
-        'notifications': {'enabled': true},
-      };
       final JsonCacheLocalStorage jsonCache = _fakeInstance;
       await jsonCache.refresh(profKey, profData);
       await jsonCache.refresh(prefKey, prefData);
diff --git a/test/json_cache_mem_test.dart b/test/json_cache_mem_test.dart
index aecb4c3..49d0659 100644
--- a/test/json_cache_mem_test.dart
+++ b/test/json_cache_mem_test.dart
@@ -111,11 +111,6 @@ void main() {
       });
     });
     test('contains', () async {
-      final profData = <String, dynamic>{'id': 1, 'name': 'John Due'};
-      final prefData = <String, dynamic>{
-        'theme': 'dark',
-        'notifications': {'enabled': true},
-      };
       final memCache = JsonCacheMem();
       // update data
       await memCache.refresh(profKey, profData);
@@ -130,6 +125,14 @@ void main() {
       expect(await memCache.contains(prefKey), false);
       expect(await memCache.contains('a key'), false);
     });
+    test('keys', () async {
+      final memCache = JsonCacheMem();
+      // update data
+      await memCache.refresh(profKey, profData);
+      await memCache.refresh(prefKey, prefData);
+
+      expect(await memCache.keys(), [profKey, prefKey]);
+    });
     group('remove', () {
       test('default ctor', () async {
         final JsonCacheMem memCache = JsonCacheMem();
diff --git a/test/json_cache_safe_local_storage_test.dart b/test/json_cache_safe_local_storage_test.dart
index be7eb47..98d7d5f 100644
--- a/test/json_cache_safe_local_storage_test.dart
+++ b/test/json_cache_safe_local_storage_test.dart
@@ -123,6 +123,13 @@ void main() {
         },
       );
 
+      test('keys', () async {
+        // update data
+        await jsonCacheSafeLocalStorage.refresh(profKey, profData);
+        await jsonCacheSafeLocalStorage.refresh(prefKey, prefData);
+
+        expect(await jsonCacheSafeLocalStorage.keys(), [profKey, prefKey]);
+      });
       test(
         'clear',
         () async {
diff --git a/test/json_cache_shared_preferences_test.dart b/test/json_cache_shared_preferences_test.dart
index b31e374..c0172af 100644
--- a/test/json_cache_shared_preferences_test.dart
+++ b/test/json_cache_shared_preferences_test.dart
@@ -5,9 +5,14 @@ import 'package:shared_preferences/shared_preferences.dart';
 void main() {
   SharedPreferences.setMockInitialValues({});
   group('JsonCacheSharedPreferences', () {
+    const profKey = 'profile';
+    const prefKey = 'preferences';
+    const profData = <String, dynamic>{'id': 1, 'name': 'John Due'};
+    const prefData = <String, dynamic>{
+      'theme': 'dark',
+      'notifications': {'enabled': true},
+    };
     test('clear, value, refresh', () async {
-      const profKey = 'profile';
-      const profData = <String, Object>{'id': 1, 'name': 'John Due'};
       final JsonCacheSharedPreferences prefsCache =
           JsonCacheSharedPreferences(await SharedPreferences.getInstance());
       await prefsCache.refresh(profKey, profData);
@@ -19,13 +24,6 @@ void main() {
     });
 
     test('contains', () async {
-      const profKey = 'profile';
-      const prefKey = 'preferences';
-      final profData = <String, dynamic>{'id': 1, 'name': 'John Due'};
-      final prefData = <String, dynamic>{
-        'theme': 'dark',
-        'notifications': {'enabled': true},
-      };
       final JsonCacheSharedPreferences prefs =
           JsonCacheSharedPreferences(await SharedPreferences.getInstance());
       // update data
@@ -43,14 +41,17 @@ void main() {
       await prefs.remove(prefKey);
       expect(await prefs.contains(prefKey), false);
     });
+
+    test('keys', () async {
+      final JsonCacheSharedPreferences prefs =
+          JsonCacheSharedPreferences(await SharedPreferences.getInstance());
+      // update data
+      await prefs.refresh(profKey, profData);
+      await prefs.refresh(prefKey, prefData);
+
+      expect(await prefs.keys(), [profKey, prefKey]);
+    });
     test('remove', () async {
-      const profKey = 'profile';
-      const prefKey = 'preferences';
-      final profData = <String, Object>{'id': 1, 'name': 'John Due'};
-      final prefData = <String, Object>{
-        'theme': 'dark',
-        'notifications': {'enabled': true},
-      };
       final JsonCacheSharedPreferences prefsCache =
           JsonCacheSharedPreferences(await SharedPreferences.getInstance());
       await prefsCache.refresh(profKey, profData);
diff --git a/test/json_cache_try_test.dart b/test/json_cache_try_test.dart
index 1f0cb68..b0f375d 100644
--- a/test/json_cache_try_test.dart
+++ b/test/json_cache_try_test.dart
@@ -42,6 +42,20 @@ void main() {
       // Check if the interaction occurred only once.
       verify(() => jsonCacheMock.contains('aKey')).called(1);
     });
+    test('keys should throw "JsonCacheException"', () async {
+      final JsonCacheTry jsonCacheTry = JsonCacheTry(jsonCacheMock);
+      // Stub the 'contains' method.
+      when(() => jsonCacheMock.keys()).thenThrow(Exception('Cache Failure'));
+      // Verify no interactions have occurred.
+      verifyNever(() => jsonCacheMock.keys());
+      // Interact with the jsonCacheTry instance.
+      expect(
+        () async => jsonCacheTry.keys(),
+        throwsA(const TypeMatcher<JsonCacheException>()),
+      );
+      // Check if the interaction occurred only once.
+      verify(() => jsonCacheMock.keys()).called(1);
+    });
     test('refresh should throw "JsonCacheException"', () async {
       final JsonCacheTry jsonCacheTry = JsonCacheTry(jsonCacheMock);
       // Stub the 'refresh' method.
diff --git a/test/json_cache_wrap_test.dart b/test/json_cache_wrap_test.dart
index a48148a..fa24736 100644
--- a/test/json_cache_wrap_test.dart
+++ b/test/json_cache_wrap_test.dart
@@ -9,6 +9,11 @@ void main() {
   group('JsonCacheWrap', () {
     const profKey = 'profile';
     const prefKey = 'preferences';
+    const profData = <String, dynamic>{'id': 1, 'name': 'John Due'};
+    const prefData = <String, dynamic>{
+      'theme': 'dark',
+      'notifications': {'enabled': true},
+    };
     group('clear, value and refresh', () {
       test('default ctor', () async {
         const Map<String, dynamic> data = <String, dynamic>{
@@ -25,11 +30,6 @@ void main() {
       });
     });
     test('contains', () async {
-      final profData = <String, dynamic>{'id': 1, 'name': 'John Due'};
-      final prefData = <String, dynamic>{
-        'theme': 'dark',
-        'notifications': {'enabled': true},
-      };
       final wrap = JsonCacheTestWrap();
 
       // update data
@@ -45,12 +45,16 @@ void main() {
       expect(await wrap.contains(prefKey), false);
       expect(await wrap.contains('a key'), false);
     });
+    test('keys', () async {
+      final wrap = JsonCacheTestWrap();
+
+      // update data
+      await wrap.refresh(profKey, profData);
+      await wrap.refresh(prefKey, prefData);
+
+      expect(await wrap.keys(), [profKey, prefKey]);
+    });
     test('remove', () async {
-      final profData = <String, dynamic>{'id': 1, 'name': 'John Due'};
-      final prefData = <String, dynamic>{
-        'theme': 'dark',
-        'notifications': {'enabled': true},
-      };
       final wrap = JsonCacheTestWrap();
       await wrap.refresh(profKey, profData);
       await wrap.refresh(prefKey, prefData);