Added tests for NT4 connections

lib/services/nt4.dart

@@ -28,6 +28,9 @@ class NT4Client {
 
   WebSocketChannel? _ws;
 
+  Map<int, NT4Subscription> get subscriptions => _subscriptions;
+  Set<NT4Subscription> get subscribedTopics => _subscribedTopics;
+
   NT4Client({
     required this.serverBaseAddress,
     this.onConnect,

test/services/ds_interop_test.dart

@@ -0,0 +1,8 @@
+import 'package:elastic_dashboard/services/ds_interop.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  test('DS Interop', () {
+    DSInteropClient();
+  });
+}

test/services/nt4_test.dart

@@ -0,0 +1,60 @@
+import 'package:elastic_dashboard/services/nt4.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  test('NT4 Client', () {
+    bool connected = false;
+
+    NT4Client client = NT4Client(
+      serverBaseAddress: '10.3.53.2',
+      onConnect: () => connected = true,
+      onDisconnect: () => connected = false,
+    );
+
+    expect(connected, false);
+
+    // Subscribing
+    NT4Subscription subscription1 =
+        client.subscribe('/SmartDashboard/Test Number');
+
+    expect(client.subscriptions.length, greaterThanOrEqualTo(1));
+
+    expect(client.lastAnnouncedValues.isEmpty, true);
+
+    // Publishing and adding to the last announced values
+    client.addSample(
+        NT4Topic(
+            name: '/SmartDashboard/Test Number',
+            type: NT4TypeStr.kFloat32,
+            properties: {}),
+        3.53);
+
+    expect(client.lastAnnouncedValues.isEmpty, false);
+
+    expect(subscription1.currentValue != null, true);
+
+    NT4Subscription subscription2 =
+        client.subscribe('/SmartDashboard/Test Number');
+
+    // If the subscriptions are shared
+    expect(client.subscribedTopics.length, 1);
+
+    client.unSubscribe(subscription1);
+
+    expect(client.subscribedTopics.length, 1);
+
+    client.unSubscribe(subscription2);
+
+    expect(client.subscribedTopics.length, 0);
+
+    // Changing ip address
+    expect(client.lastAnnouncedValues.isEmpty, false);
+
+    client.setServerBaseAddreess('10.26.01.2');
+
+    expect(client.serverBaseAddress, '10.26.01.2');
+
+    expect(client.announcedTopics.isEmpty, true);
+    expect(client.lastAnnouncedValues.isEmpty, true);
+  });
+}