20.3. Preparing an Application for Testing

Vaadin TestBench can usually test Vaadin applications as they are, especially if just taking screenshots. However, assertions on HTML elements require a DOM path to the element and this path is vulnerable to even small changes in the DOM structure. They might change because of your layout or UI logic, or if a new Vaadin version has some small changes. To make such problems less common, you can use debug IDs to refer to components.

public class ApplicationToBeTested extends Application {
    public void init() { 
        final Window main = new Window("Test window");
        setMainWindow(main);
        
        // Create a button
        Button button = new Button("Push Me!");
        
        // Optional: give the button a unique debug ID
        button.setDebugId("main.button");
        
        // Do something when the button is clicked
        button.addListener(new ClickListener() {
            @Override
            public void buttonClick(ClickEvent event) {
                // This label will not have a set debug ID
                main.addComponent(new Label("Thanks!"));
            }
        });
        main.addComponent(button);
    }
}