TooltipWidgetImpl extends PopupPanel implements TooltipWidget { @Override public void setDescription(@NotNull String description) { this.description.setText(description); } @Inject  TooltipWidgetImpl(); @Override void setDescription(@NotNull String description); @UiField
    public Label description; }
@Test public void descriptionShouldBeSet() throws Exception { tooltip.setDescription(SOME_TEXT); verify(tooltip.description).setText(SOME_TEXT); }