HelpIcon extends Composite { public void setHelpContent(final String content) { popover.setContent(content); popover.reconfigure(); } HelpIcon();   HelpIcon(Icon icon,
             SimplePanel panel,
             Popover popover); void setHelpTitle(final String title); void setHelpContent(final String content);  }
@Test public void setHelpContent() { helpIcon.setHelpContent("testContent"); verify(popover).setContent("testContent"); }