Fix vaadin latest test (#9694)

instrumentation/vaadin-14.2/testing/src/main/java/test/vaadin/MainView.java

@@ -10,6 +10,7 @@ import com.vaadin.flow.component.button.Button;
 import com.vaadin.flow.component.html.Label;
 import com.vaadin.flow.component.orderedlayout.VerticalLayout;
 import com.vaadin.flow.router.Route;
+import java.lang.reflect.Method;
 
 @Route("main")
 public class MainView extends VerticalLayout {
@@ -19,8 +20,18 @@ public class MainView extends VerticalLayout {
   public MainView() {
     Label label = new Label("Main view");
     label.setId("main.label");
-    Button button = new Button("To other view", e -> UI.getCurrent().navigate(OtherView.class));
+    Button button = new Button("To other view", e -> navigate(OtherView.class));
     button.setId("main.button");
     add(label, button);
   }
+
+  private static void navigate(Class<?> navigationTarget) {
+    try {
+      // using reflection because return type of the method changes from void to Optional
+      Method method = UI.class.getMethod("navigate", Class.class);
+      method.invoke(UI.getCurrent(), navigationTarget);
+    } catch (Exception exception) {
+      throw new IllegalStateException(exception);
+    }
+  }
 }