How to get selenium to wait for ajax response?

I would use

waitForElementPresent(locator)

This will wait until the element is present in the DOM.

If you need to check the element is visible, you may be better using

waitForElementHeight(locator)

A more general solution than waiting for an element would be to wait for all the connections to the server to close. This will allow you to wait for all ajax calls to finish, even if they don't have any callback and thus don't affect the page. More details can be found here.

Using C# and jQuery, I have created the following method to wait for all AJax calls to complete (if anyone have more direct ways of accessing JS variables from C#, please comment):

internal void WaitForAjax(int timeOut = 15){    var value = "";    RepeatUntil(        () => value = GetJavascriptValue("jQuery.active"),         () => value == "0",         "Ajax calls did not complete before timeout"    );}internal void RepeatUntil(Action repeat, Func<bool> until, string errorMessage, int timeout = 15){    var end = DateTime.Now + TimeSpan.FromSeconds(timeout);    var complete = false;    while (DateTime.Now < end)    {        repeat();        try        {            if (until())            {                complete = true;                break;            }        }        catch (Exception)        { }        Thread.Sleep(500);    }    if (!complete)        throw new TimeoutException(errorMessage);}internal string GetJavascriptValue(string variableName){    var id = Guid.NewGuid().ToString();    _selenium.RunScript(String.Format(@"window.$('body').append(""<input type='text' value='""+{0}+""' id='{1}'/>"");", variableName, id));    return _selenium.GetValue(id);}

If using python, you may use this function, which clicks the button and waits for the DOM change:

def click_n_wait(driver, button, timeout=5):    source = driver.page_source    button.click()    def compare_source(driver):        try:            return source != driver.page_source        except WebDriverException:            pass    WebDriverWait(driver, timeout).until(compare_source)

(CREDIT: based on this stack overflow answer)