public void expandTab(int index) {
        WebElement tab = getHeaders().get(index);
        if (tab.getDomAttribute("aria-expanded").equalsIgnoreCase("false")) {
            toggleTab(index);
        }
    }
Expands the tab denoted by the specified index.

@param index the index of the tab to expand
primefaces-selenium/primefaces-selenium-components/src/main/java/org/primefaces/selenium/component/AccordionPanel.java