Using the Sencha Test Studio to Test my GXT App... Here is a quick example of how to wire up a Suite for Sencha Studio.

Gxt4SandboxProjectEntryPoint.java

public class Gxt4SandboxProjectEntryPoint implements EntryPoint {

  private HTML label;

  @Override
  public void onModuleLoad() {
    ContentPanel northWidget = new ContentPanel();
    northWidget.add(new HTML("north"));
    
    ContentPanel centerWidget = new ContentPanel();
    centerWidget.add(createCenterWidget());
    
    BorderLayoutContainer blc = new BorderLayoutContainer();
    blc.setNorthWidget(northWidget);
    blc.setWidget(centerWidget);
    
    Viewport viewport = new Viewport();
    viewport.add(blc, new MarginData(20));
    
    RootPanel.get().add(viewport);
  }

  private Widget createCenterWidget() {
    label = new HTML("Label");
    label.ensureDebugId("center-label");
    
    TextField field = new TextField();
    field.ensureDebugId("center-field");
    field.addValueChangeHandler(new ValueChangeHandler<String>() {
      @Override
      public void onValueChange(ValueChangeEvent<String> event) {
        label.setHTML("Label " + event.getValue());
      }
    });
    
    TextButton button = new TextButton("Button");
    button.ensureDebugId("center-button");
    
    VerticalLayoutContainer vlc = new VerticalLayoutContainer();
    vlc.add(label);
    vlc.add(field);
    vlc.add(button);
    
    
    return vlc;
  }
  
}

Suite.js

describe("Suite", function() {
    it("label is updated with field text", function() {
        
        // 1. When I have a field and I focus and type hello, then blur
        ST.element('@gwt-debug-center-field')
        .element('input')
        .focus()
        .type('Hello')
        .element('@gwt-debug-center-button')
        .click(10, 10);
        
         // 3. It will update the label with the field text. 
        ST.element('@gwt-debug-center-label')
        .textLike('Hello');
        
    });
});

Here's how it looks in the Sencha Test Studio

Then if you want to run it: