### Question:
FormGeneratorDriver implements LayoutGeneratorDriver { public void clear() { layoutComponents.clear(); instance.destroyAll(); wrapperWidgetUtil.clear(this); componentsCache.clear(); renderingContext = null; } @Inject  FormGeneratorDriver(SyncBeanManager beanManager, ManagedInstance<LayoutDragComponent> instance, FormsElementWrapperWidgetUtil wrapperWidgetUtil, Document document); FormRenderingContext getRenderingContext(); void setRenderingContext(FormRenderingContext renderingContext); @Override HTMLElement createContainer(); @Override HTMLElement createRow(LayoutRow layoutRow); @Override HTMLElement createColumn(LayoutColumn layoutColumn); @Override IsWidget createComponent(HTMLElement column, LayoutComponent layoutComponent); @Override Optional<IsWidget> getComponentPart(HTMLElement column, LayoutComponent layoutComponent, String partId); List<FieldLayoutComponent> getLayoutFields(); FieldLayoutComponent getFieldLayoutComponentForField(FieldDefinition field); void clear();  }### Answer:
@Test public void testClear() { driver.clear(); verify(instance).destroyAll(); verify(wrapperWidgetUtil).clear(same(driver)); }