### Question:
ZoomLevelSelectorView extends Composite implements ZoomLevelSelector.View { @Override public void dropUp() { dropDownPanelGroup.setClassName(dropDownPanelGroup.getClassName() + " " + CSS_DROP_UP); }  @Override void init(final ZoomLevelSelector presenter); @Override void add(final String text,
                    final Command onClick); @Override void clear(); void setSelectedValue(String selectedItem); @Override void setText(String text); @Override void setEnabled(boolean enabled); @Override void dropUp(); @PreDestroy void destroy();  }### Answer:
@Test public void testDropup() { when(dropDownPanelGroup.getClassName()).thenReturn("pg"); tested.dropUp(); verify(dropDownPanelGroup, times(1)).setClassName(eq("pg " + ZoomLevelSelectorView.CSS_DROP_UP)); }