How can I handle alerts that occur on page navigation with WebDriver? - selenium

Question

The scenario here is that certain pages I'm testing will have an unload event - i.e. prompt to save changes if there are unsaved changes is a common example and I want to be able to detect that and handle it.
Here is the specific problem:
I'm testing a pretty complicated web app which will allow users to edit rich content in a browser and the app will auto-save changes from the user. So this test does something like the following:
Navigate to the app
Do some edits
Navigate away
However, since the app auto-saves changes on navigating away and there are unsaved changes - this prompt will show up: http://i.stack.imgur.com/c9iP2.png
Whenever there is an alert in Selenium, the next action will fail miserably with a callstack like:
org.openqa.selenium.UnhandledAlertException: unexpected alert open
(Session info: chrome=39.0.2171.65)
(Driver info: chromedriver=2.11.298604 (75ea2fdb5c87f133a8e1b8da16f6091fb7d5321e),platform=Windows NT 6.1 SP1 x86_64) (WARNING: The server did not provide any stacktrace information)
Command duration or timeout: 87 milliseconds: null
Build info: version: '2.43.1', revision: '5163bceef1bc36d43f3dc0b83c88998168a363a0', time: '2014-09-10 09:43:55'
System info: host: 'ip-10-231-174-40', ip: '10.231.174.40', os.name: 'Linux', os.arch: 'amd64', os.version: '3.11.0-19-generic', java.version: '1.7.0_51'
Session ID: 889cbda1d1a946a38e90e4ec9f32e827
Driver info: org.openqa.selenium.remote.RemoteWebDriver
Capabilities [{platform=XP, acceptSslCerts=true, javascriptEnabled=true, hasMetadata=true, browserName=chrome, chrome={userDataDir=C:\Users\ADMINI~1\AppData\Local\Temp\scoped_dir1584_15883}, rotatable=false, mobileEmulationEnabled=false, locationContextEnabled=true, webdriver.remote.sessionid=889cbda1d1a946a38e90e4ec9f32e827, version=39.0.2171.65, takesHeapSnapshot=true, databaseEnabled=false, cssSelectorsEnabled=true, handlesAlerts=true, browserConnectionEnabled=false, nativeEvents=true, webStorageEnabled=true, applicationCacheEnabled=false, takesScreenshot=true}]
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
at org.openqa.selenium.remote.ErrorHandler.createThrowable(ErrorHandler.java:204)
at org.openqa.selenium.remote.ErrorHandler.throwIfResponseFailed(ErrorHandler.java:162)
at org.openqa.selenium.remote.RemoteWebDriver.execute(RemoteWebDriver.java:599)
at org.openqa.selenium.remote.RemoteWebDriver.execute(RemoteWebDriver.java:614)
at org.openqa.selenium.remote.RemoteWebDriver.getCurrentUrl(RemoteWebDriver.java:319)
So one solution might be that I put try/catches whenever my test navigates away from this page but I'm wondering if there is a more elegant and systematic solution (i.e. something that would either detect alerts or page navigation so they get handled).
Does anyone have a working solution for this problem?

Answer 1

You need to switch to alert and accept it. Example in Java:
Alert alert = driver.switchTo().alert();
alert.accept();
You may also need to wait for it to appear before switching:
WebDriverWait wait = new WebDriverWait(driver, 10);
wait.until(ExpectedConditions.alertIsPresent());
Alert alert = driver.switchTo().alert();
alert.accept();
Alternatively, you can stop the popup to be shown in the first place. The idea is to remove all beforeunload event listeners with javascript:
JavascriptExecutor js = (JavascriptExecutor) driver;
js.executeScript(
"window.addEventListener(\"load\", foo, false);" +
"function foo() { " +
"var u = \"beforeunload\";" +
"var v = unsafeWindow;" +
"if (v._eventTypes && v._eventTypes[u]) {" +
"var r=v._eventTypes[u];" +
"for(var s=0;s<r.length;s++) { " +
"v.removeEventListener(u,r[s],false);" +
"}" +
"v._eventTypes[u]=[];" +
"}");