feat: add test for dialog

+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:get/get.dart';
+
+import 'util/wrapper.dart';
+
+void main() {
+  testWidgets("Get.defaultDialog smoke test", (tester) async {
+    await tester.pumpWidget(
+      Wrapper(child: Container()),
+    );
+
+    Get.defaultDialog(
+        onConfirm: () => print("Ok"),
+        middleText: "Dialog made in 3 lines of code");
+
+    await tester.pumpAndSettle();
+
+    expect(find.text("Ok"), findsOneWidget);
+  });
+
+  testWidgets("Get.dialog smoke test", (tester) async {
+    await tester.pumpWidget(
+      Wrapper(child: Container()),
+    );
+
+    Get.dialog(YourDialogWidget());
+
+    await tester.pumpAndSettle();
+
+    expect(find.byType(YourDialogWidget), findsOneWidget);
+  });
+}
+
+class YourDialogWidget extends StatelessWidget {
+  const YourDialogWidget({Key key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return Container();
+  }
+}