create no connection test

test/services/robot_notifications_listener_test.dart

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+import 'package:elastic_dashboard/services/robot_notifications_listener.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:mockito/mockito.dart';
+
+import '../test_util.dart';
+import '../test_util.mocks.dart';
+
+// Create a mock class for the onNotification callback
+class MockNotificationCallback extends Mock {
+  void call(String? title, String? description, Icon? icon);
+}
+
+void main() {
+  test("Robot Notifications (No Connection) ", () {
+    MockNTConnection mockConnection = createMockOfflineNT4();
+    MockNT4Subscription mockSub = MockNT4Subscription();
+
+    when(mockConnection.subscribeAll(any, any)).thenReturn(mockSub);
+
+    // Create a mock for the onNotification callback
+    MockNotificationCallback mockOnNotification = MockNotificationCallback();
+
+    RobotNotificationsListener notifications = RobotNotificationsListener(
+      ntConnection: mockConnection,
+      onNotification: mockOnNotification.call,
+    );
+
+    notifications.listen();
+
+    // Verify that subscribeAll was called with the specific parameters
+    verify(mockConnection.subscribeAll('/Elastic/robotnotifications', 0.2))
+        .called(1);
+    verify(mockConnection.addDisconnectedListener(any)).called(1);
+
+    // Verify that no other interactions have been made with the mockConnection
+    verifyNoMoreInteractions(mockConnection);
+
+    // Verify that the onNotification callback was never called
+    verifyNever(mockOnNotification.call(any, any, any));
+  });
+}