Performance, Scalability and Architecture

Andreas Grabner

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Selenium Tests for Automated JavaScript/AJAX Performance Analysis

A step-by-step guide

With more than 3 million downloads, Selenium is a functional testing framework. It allows web developers and QA professionals to automatically test how an application functions on multiple browsers, such as Firefox, Internet Explorer and Chrome and across operating systems, such as different versions of Windows and Mac OS.

The FREE dynaTrace AJAX Edition on the other side is probably the best web site performance analysis tool for Internet Explorer 6, 7 and 8.  Here is what John Resig, Creator of jQuery has to say about it: “I’m very impressed with dynaTrace AJAX Edition’s ability to get at the underlying “magic” that happens inside a browser: page rendering, DOM method execution, browser events, and page layout calculation. Much of this information is completely hidden from developers and I’ve never seen it so easily collected into a single tool. Huge kudos to dynaTrace for revealing this information and especially so for making it happen in Internet Explorer

Combine best of breed tools for Automated Performance Analysis
If we look at these two tools it almost seems logical to use them in combination in order to automatically capture performance data from within the browser for every Selenium Test you execute.

Why would you want to do that?

In case your Selenium Tests identify a problem – whether it is a functional issue (page not working correctly) or a performance problem (page are much slower in the latest build) – the data that is automatically captured by dynaTrace AJAX contains all information necessary for your web engineers to figure out the root cause of the problem. Without this information, your engineers probably go ahead and manually reproduce the error by executing and debugging through the test case manually. Manual work means additional time and effort – and that’s what can be avoided. Best of all – BOTH TOOLS ARE FREE!!

How it works – Example on testing Google Search
Selenium has multiple options to execute tests. Either use your HTML Test Suites that define the individual test cases in HTML Tables or use a programming language such as Java and “code” your tests. Let’s have a look at these two scenarios and how you can get Selenium to work with the dynaTrace AJAX Edition.

The integration basics are explained in Automation with dynaTrace AJAX Edition and  in Advanced Timing and Argument Capturing. The dynaTrace AJAX Agent that runs as an Internet Explorer Add-On gets activated and is configurable via several environment variables. DT_IE_AGENT_ACTIVE=true activates the Add-On so that it collects data from the current browser session. DT_IE_SESSION_NAME can be used to specify the recorded session name, e.g.: MySeleniumTest123. DT_IE_SERVER_HOST and DT_IE_SERVER_PORT can be used to connect to a dynaTrace AJAX Edition client that runs on a different machine – this is useful when you want to centralize data capturing. DT_IE_CLEAR_CACHE=true causes the Add-On to clear the browser cache before any actions are executed – this is very useful when you want to test your web sites cache behaviour.

These environment variables need to be set for the browser instance that runs the tested website. The browser is launched by the selenium server process. Therefore we have to set these environment variables for that server process as they are propagated to all processes that get launched from it.

Requirement: The dynaTrace AJAX Edition must be running on the local machine in order for the launched browser instances to connect to it. You can also run the AJAX Edition on a different machine – in this case you need to specify DT_IE_SERVER_NAME with the name of the machine where the AJAX Edition runs on.

Running an HTML Test Suite
The following batch file sets the necessary environment variables to a) activate the dynaTrace AJAX Add-On in IE and b) specifiy a custom session name:

@echo off
set SELENIUM_RC=C:\selenium\selenium-server.jar
set SCRIPT_PATH=%~dp0

rem dynaTrace AJAX IE agent settings
set DT_IE_SESSION_NAME=Google_SeleniumTest

java -jar %SELENIUM_RC% -log exec.log -htmlSuite "*iexplore" ""
"%SCRIPT_PATH%\GoogleSuite.html" "%SCRIPT_PATH%\GoogleResults.html"

Before I run this script I make sure to launch the dynaTrace AJAX Edition. When I execute the script Selenium will launch the HtmlRunner in a separate browser instance and will then launch the browser that will execute your test steps. The second browser instance will have the active dynaTrace AJAX agent. You can tell this by the changed IE icon as well as an increasing number in the Captured Events displayed in the dynaTrace AJAX Edition IE Toolbar:

Executing an HTML Test Suite with dynaTrace AJAX capturing  performance data

Executing an HTML Test Suite with dynaTrace AJAX capturing performance data

Note: Even though both browser instances use the DT_IE_XXX environment variables, the AJAX Edition will not collect information from the Selenium Test Runner. The Test Runner runs as an HTA Application which prevents the AJAX Edition Add-On from being loaded. In this case it is an advantage as we are not interested in the performance of the Selenium Runner.

Once the test is done and the browser is closed we can explore the results captured in the dynaTrace AJAX Edition:

dynaTrace AJAX Edition captured performance data from the Selenium  Test Run using the configured Session Name

dynaTrace AJAX Edition captured performance data from the Selenium Test Run using the configured Session Name

The session name is the one we passed in via DT_IE_SESSION_NAME – Google_SeleniumTest in this case. You will see a URL to a local file. That is a file that Selenium opens which then actually opens the URL of the test application. Simply ignore this line and focus on those URLs of your test scenario.

Running Test Case from Java (or JUnit)
Many folks out there use the option to write their Selenium tests in Java – either using JUnit as executing framework or just using the DefaultSelenium proxy in a console app or custom test framework. The approach here is the same as explained in the Html Test Case Use Case. We have to start the selenium server with the DT_IE_XXX environment variables. Here is the batch file I use:

@echo off
set SELENIUM_RC=C:\selenium\selenium-server.jar
set SCRIPT_PATH=%~dp0

rem IE agent settings
set DT_IE_SESSION_NAME=dynaTrace_Selenium

java -jar %SELENIUM_RC%

Here is my Java application that executes the same Google Search test steps as my HTML Test Suite:

public static void main(String args[]) {
Selenium selenium
= new DefaultSelenium("localhost", 4444, "*iexplore", "");

type("q", "dynatrace");


The result is the same. The Selenium server launches two browser instances. The first loads the Selenium Runner which won’t be analyzed by dynaTrace AJAX as it is an HTA Application. The second launches and searches for dynaTrace. The following screenshot shows this captured session with the name dynaTrace_Selenium:

dynaTrace AJAX Edition captured the data from the test steps  executed by my Java application

dynaTrace AJAX Edition captured the data from the test steps executed by my Java application

Where to go from here?
The feedback I get from our user community is that this type of integration is a huge time saver. Whenever their Selenium tests fail, the in-depth performance data from the test run is available for analysis. A key point to remember is that this is not just about performance. As the AJAX Edition captures full JavaScript traces, DOM Access, Network and Rendering activities, it makes it very easy to identify all functional and deployment-related problems. Analyzing the dynaTrace AJAX data allows one to identify whether the problem is caused by files that didn’t get deployed on the web server, whether a new JavaScript library was introduced that wasn’t fully tested yet, or whether the problem actually originates on the server-side code. Check out the following additional resources to learn more about how to analyze the data that is captured: Getting Started with dynaTrace AJAX Edition (includes links to real-life web site analysis examples), Why Web 2.0 requires full End-to-End visibility and Learn how uses the AJAX Edition for their web-site

In case you have questions on this topic, either comment on the blog or use the comment feature on our dynaTrace AJAX Community Portal.

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More Stories By Andreas Grabner

Andreas Grabner has been helping companies improve their application performance for 15+ years. He is a regular contributor within Web Performance and DevOps communities and a prolific speaker at user groups and conferences around the world. Reach him at @grabnerandi