Selenium: are there events like “New element inserted in DOM”

问题

The site I am testing has a notification logic that brings up a message at the bottom of the screen, keeps it there for one second and then sends it away. When the notification is displayed it hides other elements and that makes my test unstable. I did my best to figure out when the notification is displayed (when the business logic displays it) and dismiss it but every now and then I detect new cases my code are not aware of when the notification is displayed.

Is there a way (using Selenium) to subscribe to an event like "New element inserted in DOM". Dismissing the notification on its callback would solve my problem once and for all.

回答1:

Selenium doesn't support this use case out of the box but you can achieve that using MutationObserver in javascript. I don't know what language you are using to write selenium test but in C# you can create extensions method as follow

public static void StartWatchingForContentChange(this RemoteWebDriver driver, string containerId, int  timeout = SearchElementDefaultTimeout)
{
    driver.ExecuteScript(@"var $$expectedId = arguments[0];
__selenium_observers__ =  window.__selenium_observers__ || {};
(function(){        
var target = document.getElementById($$expectedId);
__selenium_observers__[$$expectedId] = {
        observer: new MutationObserver(function(mutations) {
            __selenium_observers__[$$expectedId].occured = true;
            __selenium_observers__[$$expectedId].observer.disconnect();
        }),
        occured:false
};
var config = { attributes: true, childList: true, characterData: true, subtree: true };
__selenium_observers__[$$expectedId].observer.observe(target, config);
})();", containerId);       
}

public static bool WasContentChanged(this RemoteWebDriver driver, string containerId)
{
    return (bool) driver.ExecuteScript( "return window.__selenium_observers__ && window.__selenium_observers__[arguments[0]].occured;", containerId)
}

You can use some kind of timer to asynchronously invoke WasContentChanged method and react for content changes. Please read MutationObserver documentation for more details https://developer.mozilla.org/pl/docs/Web/API/MutationObserver

来源：https://stackoverflow.com/questions/41192258/selenium-are-there-events-like-new-element-inserted-in-dom