public void canOnlyClickVisibleElement() {
WebElement navBar = driver.findElement(By.tagName("UIANavigationBar"));
Assert.assertTrue(navBar.isDisplayed(), "nav bar");
navBar.click();
List<WebElement> imgs = navBar.findElements(By.className("UIAImage"));
Assert.assertEquals(imgs.size(), 2, "number of images in the menu");
for (WebElement el : imgs) {
Assert.assertFalse(el.isDisplayed(), "image");