tests and mocks for e2e testing (#78)

* tests and mocks for e2e testing

* formatting

* fix analyze errors

test/mock/websocket_mock.dart

@@ -0,0 +1,22 @@
+import 'package:livekit_client/src/support/websocket.dart';
+
+class MockWebSocket extends LiveKitWebSocket {
+  @override
+  void send(List<int> data) {}
+}
+
+class MockWebSocketConnector {
+  WebSocketEventHandlers? handlers;
+
+  WebSocketOnData get onData => handlers!.onData!;
+
+  WebSocketOnDispose get onDispose => handlers!.onDispose!;
+
+  WebSocketOnError get onError => handlers!.onError!;
+
+  Future<LiveKitWebSocket> connect(Uri uri,
+      [WebSocketEventHandlers? options]) async {
+    handlers = options;
+    return MockWebSocket();
+  }
+}