### Question:
ApplicationCore { public void attach() { if (!attached) { try { runtimeAgg.start(); attached = true; if (CREATE_MOCK_RAINBOW) { mockRainbow.run(); } } catch (RuntimeAggregatorException ex) { Logger.getLogger(ApplicationCore.class.getName()).log(Level.SEVERE, "Cannot attach to the Rainbow system.", ex); } } } protected  ApplicationCore(); static ApplicationCore getInstance(); void startup(String filename); void attach(); void detach(); String getWriteSession(); ArrayList<String> getSessionList(); boolean isAttached(); static void registerWidgets(); IRuntimeAggregator<?> getRuntimeAggregator(); ISystemConfiguration getSystemConfiguration(); ArrayList<String> getViewConfigurations(); ViewConfiguration getViewConfiguration(String name); String getLatestViewConfigurationName(); void saveViewConfiguration(ViewConfiguration config, String name);  }### Answer:
@Test public void testAttach() { instance.attach(); assertEquals(instance.isAttached(), true); }