Take a screenshot on exception with Selenium C#'s EventFiringWebDriver

Published: by Creative Commons Licence

Apart from concrete browser's WebDriver implementations like FirefoxDriver, ChromeDriver, PhantomJSDriver, etc., Selenium C# binding also provides one other type of driver called EventFiringWebDriver, which wraps around any WebDriver instance and supports registering for events, e.g. for logging things that WebDriver has been doing.

This class inherits from IWebDriver interface but additionally provides events like Navigating, ElementClicking, ExceptionThrown etc. It can be found within Selenium's support library WebDriver.Support.dll (under namespace "OpenQA.Selenium.Support.Events"). The source code is here and the related tests exist here.

Below gives an example of how to take a screenshot when an exception is thrown while executing WebDriver tests using Selenium C# binding's EventFiringWebDriver class. Since the driver instance is a type of EventFiringWebDriver, whenever an exception is thrown, ExceptionThrown event will be triggered and a screenshot should be taken.

A completed example solution has been created on GitHub in this repository. Code has been tested under environment Windows 7, Firefox 26 with Selenium 2.39.0.

private IWebDriver driver;

public void FooMethod() {
    var firingDriver = new EventFiringWebDriver(new FirefoxDriver());
    firingDriver.ExceptionThrown += firingDriver_TakeScreenshotOnException;

    driver = firingDriver;

    // try find a non-existent element where NoSuchElementException should be thrown
    driver.FindElement(By.CssSelector("#some_id .foo")); // a screenshot should be taken automatically

private void firingDriver_TakeScreenshotOnException(object sender, WebDriverExceptionEventArgs e) {
    string timestamp = DateTime.Now.ToString("yyyy-MM-dd-hhmm-ss");
    driver.TakeScreenshot().SaveAsFile("Exception-" + timestamp + ".png", ImageFormat.Png);