### Question:
TabSheetArea extends VerticalLayout implements Area { protected List<Page> getTabs() { return StreamUtil.stream(() -> tabSheet.iterator()) .filter(c -> c instanceof Page) .map(c -> (Page)c) .collect(Collectors.toList()); } TabSheetArea();  TabSheetArea(boolean preserveHeader); @PostConstruct final void init(); TabSheet getTabSheet(); @Override void reloadBindings();  }### Answer:
@Test public void testGetTabs() { Page tabPage1 = mock(Page.class); Page tabPage2 = mock(Page.class); TabSheetArea tabSheetArea = new TestArea(); assertThat(tabSheetArea.getTabs(), is(empty())); tabSheetArea.addTab(tabPage1, "1"); tabSheetArea.addTab(tabPage2, "2"); assertThat(tabSheetArea.getTabs(), contains(tabPage1, tabPage2)); }