All details and the full download can be found here: https://lab.xceptance.de/releases/xlt/4.1.6/

So, for the first time we tested a non-Latin website, precisely an Arabic one. We created a test case with the Script Developer to test an Arabic news website. The test entered Arabic words in a search field and validated the response to check the correctness of the website’s content. Afterwards, we ran the script as a JUnit Test in Eclipse. It was successful. The test was short, but provisionally it proved that XLT  also works for non-Latin websites.

Furthermore, we ran the same test in a real browser and it worked as well. We used the FirefoxDriver to simulate user-like actions in Firefox to see if the WebDriver also works with non-Latin input.

When we continued testing, we observed some facts that may interest people who don’t often use Arabic as an input language. As you might know, Arabic is written from right to left. We noticed that there’s a difference between what appears and what actually happens technically. The following example illustrates that.

Placement of the Asterisk

We inserted a text assertion command in the test case. It was an ends-with validation, i.e. the asterisk should be at the first position if the input language is Latin. So, theoretically, if the input language is Arabic, then the asterisk should be at the first position of the Arabic text (the far right), but that wasn’t the case. The asterisk was at the first position from the Latin point of view (the far left).

Then, we tried inserting the asterisk at the first position of the Arabic text (the far right), but as you can see in the figure below the evaluation failed because the asterisk’s encoding is Latin-1, and accordingly the first position is then the far left according to the computer. So, we tried to insert the asterisk in Arabic (as input language), but the evaluation failed, as well.

The next picture shows how it should be.

It was really hard trying to switch our way of thinking to the “right way”.  We spent so much time trying to figure out how to insert the asterisks in the test cases and trying to understand the Arabic point of view.

Not all Asterisks are the same

So, in this case the asterisk must be inserted in Latin. Firstly, the asterisk will be inserted at the last position of the Arabic text and secondly, it has another code. As it turns out, the Arabic asterisk does not have the same code as the Latin asterisk. The Latin asterisk’s code in Unicode code points is U+002A and the Arabic one’s is U+066D, and it even has another name. It is called “Arabic Five Pointed Star” and it actually looks differently. You might be wondering why that is. We asked ourselves the same thing, and we couldn’t find any plausible answer.  Of course, there are different characters in Arabic such as the comma (Arabic comma: “،”), but the asterisk is pretty much an asterisk everywhere and we wondered why it is a different character code.

In the following example we wrote a very simple website as an example to check if the position of the asterisks is always on the wrong side (seen from the Arabic point of view).

At the beginning it is important to set the “charset” to Unicode or you’ll just get question marks as output. As you can see, we set in the head tag the direction of the text alignment to “rtl”- this means “from right to left”- so that the output on the website would appear from right to left. This also applies to the input field in line 13. As you may notice, there’s an exclamation mark added in Latin that’s why it’s shown at the beginning of the Arabic word because it’s technically the last position in Latin. The following picture shows how it appears in the browser.

We decided to write the text in different HTML elements (here: div and span elements) to see if it makes a difference or not if the tested text is over multiple elements. As it turned out, it has no affect if the text is over multiple elements or not and it will be output in the right order, but the problem that the position of the asterisk is wrong to the eyes of an Arab still remains, which may cause great confusion.

Parameters in Western encoding preferred

There’s also a small disadvantage for Arabic developers. Parameter names cannot be put in Arabic. Because our tool only accepts characters “A”-”Z”, “a”-”z”, “0″-”9″ and “_” for parameter names. That goes for test case names, as well. If you export your test cases with the Script Developer and you change the parameter names to Arabic in Eclipse, your test will fail unless you change the parameters in the data files as well, and then it will work just fine. The Script Developer will also show the modified Arabic parameter names and it will replay without any trouble. But if you check the parameter names in the Script Developer, you’ll notice that the name field is empty.

Programming in Arabic

Unfortunately, Arabic isn’t really supported in Eclipse on Windows, even if you run Eclipse in an Arabic version because it’s just a translated version of the platform and the operating system’s encoding is set to ISO Latin-1, i.e. any output in the console that is non-Latin will only be displayed as question marks. But in Linux it works because it supports UTF-8.

We were surprised that the Arabic version could align the Arabic text to the (far) right where it actually should begin, which is not supported by the Latin version of Eclipse. So, if you’re planning on developing a non-Latin website in Eclipse and you stumble upon a version of Eclipse in your language and decide to give it a try don’t get your hopes up because these versions are just translated, and might even be incomplete.

To sum up, we expanded our horizon by proving that our tool could also do test automation problem-free on non-Latin websites.

So what to do, when you do not know every detail about the current or future load pattern? We are describing one approach below that was very successful so far and always yielded satisfying results.

What we need

• Visits per peak hour (example 10k)
• Page views per peak hour (example 100k)
• Orders per peak hour (example 200 orders)
• Optionally we can use the conversion rate to get from visits to orders or vice versa.
• Optionally we can take searches, “add to cart” operations, user registrations, and so on into account.

The mentioned scenarios are typical ecommerce scenarios and look like that. We will not talk about smaller scenarios such as address editing for a registered user.

• TSingleClickVisit: Enters the store only, does not move beyond the start page
• TBrowsing: TVisitor plus category and product browsing
• TSearch: TVisitor plus keyword search plus browsing of the result
• TAdd2Cart: TBrowsing plus add to cart operations
• TGuestCheckout: TAdd2Cart plus checkout without an order placement (anonymous user)
• TGuestOrder: TAdd2Cart plus full checkout (anonymous user)
• TRegisteredCheckout: TAdd2Cart plus checkout without an order placement (registered customer)
• TRegisteredOrder: TAdd2Cart plus full checkout (registered customer)
• TRegistration: Account creation

What we assume

Ecommerce sites follow similar patterns and with a few exceptions, such as special promotions, certain behavioral patterns are nearly identical. So for instance, about 50% of all checkouts are stopped before the order is placed. About 20 to 50% of all created carts aren’t checked out at all.

What we calculate

Based on these assumptions, we put together a fairly simple but sufficiently accurate load mix. Of course, we can also analyze the current log files and try to come up with something more precise, but that will be a snapshot only. Traffic is very volatile and so we should be very generous when setting up this mix.

Since we do not take any daily averages as base but the peaks, we will have a pretty comfortable buffer for our daily ecommerce life anyway.

Bottom-Up

Let’s say, 200 orders are set as goal. Splitting them 50/50  between registered and anonymous users, we get 100 visits of each type. All numbers are per hour of course.

• TGuestOrder = 100
• TRegisteredOrder = 100

As a next step, we take our 50% checkout abandonment rate into account. We have 200 checkouts per hour that are stopped and 200 that run through and turn up as orders (as counted previously). So we need to add 200 visits. And because these visitors can either run with their preset account or without, we split them up in 100 guest and 100 registered checkout attempts.

• TGuestCheckout = 100
• TRegisteredCheckout = 100
  
• TGuestOrder = 100
• TRegisteredOrder = 100

This gives us 400 visits per hour that go into the checkout. We now assume a low cart to checkout conversion rate, about 20% for instance, and so we take 400 checkout visits * 5 and get 2,000 visits that involve cart usage. Since we already have 20% converted into checkouts, we have 2,000 minus 400 visits that use the cart.

• TAdd2Cart = 1,600
• TGuestCheckout = 100
• TRegisteredCheckout = 100
• TGuestOrder = 100
• TRegisteredOrder = 100

We also know that many users do not continue after hitting the home page or any landing page. Let’s add some of these users now.

• TSingleClickVisitor = 1,000
• TAdd2Cart = 1,600
• TGuestCheckout = 100
• TRegisteredCheckout = 100
• TGuestOrder = 100
• TRegisteredOrder = 100

But wait, what are we missing? Well, we have not registered any new accounts yet. Didn’t we? We did, because the registered checkout creates accounts if required and reuses them several times. But to get a more substantial customer growth, we simply add 200 visits that run registrations:

• TRegistration = 200
• TSingleClickVisitor = 1,000
• TAdd2Cart = 1,600
• TGuestCheckout = 100
• TRegisteredCheckout = 100
• TGuestOrder = 100
• TRegisteredOrder = 100

What is left to do? Well, we do not have any “I am just looking around”-visitors yet. We know that our total visit count is 10,000 and we already assigned 3,200 of these to cart, checkout, and registration, so we have 6,800 visits left we can now use for something else. Depending on the shop type (large store, small store etc), people tend to use search more or less. To put enough stress on search and refinements, we simply assume 50% of all people like to search. Thus the missing 6,800 visits will be 3,400 catalog browser visits and 3,400 visits with usage of search before browsing the search result.

The total mix is:

• TBrowsing = 3,400
• TSearch = 3,400
• TRegistration = 200
• TSingleClickVisitor = 1000
• TAdd2Cart = 1,600
• TGuestCheckout = 100
• TRegisteredCheckout = 100
• TGuestOrder = 100
• TRegisteredOrder = 100

Wait… where are my concurrent users? This is simple: “concurrent users” is an inaccurate way of describing traffic, so we have not used that number yet. Why is that?

To get to the bottom of that, we simply check how long a visit takes. Depending on the shop, an average visit might take 2 to 4 minutes. Successfully shopping might take 15 minutes. If we expect about 10 page views per visit and a page view takes 1 second to load and 20 seconds to read it (already a really really high number for an average), a visit would take 10 * 1 second + 9 * 20 seconds = 190 seconds.

Let’s go with the 190 seconds for a visit on average. If we just could serve one visitor at a time, we could serve 60 minutes (3600 seconds) / 190 seconds per visits = 19 visitors per hour. But because we would like to serve 10,000 per hour, we have to deal with 10,000 / 19 = 526 visitors at the same time. This is the famous concurrent user number.

If we now double the think time, we have 1,052 concurrent users/visitors. If we cut it down to 1 second think time, we will get a visit length of 19 seconds and therefore 10,000 visits / (3600 seconds / 19) = 53 concurrent visitors.

So we already have three different “concurrent user” numbers and are still simulating the same traffic. This shows that the number of concurrent users is a pretty questionable way of describing traffic.

It does not matter which number we take, because most of the time the servers will see the same traffic. Because we run against a SaaS environment that serves a multiple of other customers at the same time and is sized to serve the peak traffic for all customers at the same time, we have plenty of comfortable room around us. This permits us to run with 53 concurrent visitors for most of the testing. This will save us client hardware resources for the load generation. e.g. saves us money. We are basically only interested in the runtime of requests and not if the environment can handle that, because it can.

The goal of this test is to demonstrate that the implementation on the SaaS platform is efficient, not that the SaaS platform itself is fast and stable, because this is guaranteed by design and contract. Testing this would require way more traffic and generate huge costs, because the environment would suddenly no longer be a shared one but exclusively used for this testing purpose.

When finalizing the entire test and all tests turned out good, we are going to turn up the concurrent user count to 530 users and compare the result with the previous measurements. Just to satisfy the traditional test expectations.

Does that work for you?

Hope that gives you an idea how to come up with a nice user mix for testing without having too much data in the first place. Comments welcome.

• EU-West: ami-772b1d03
• US-East: ami-52649b3b
• US-West: ami-29bfec6c

Images can be used free of charge. The EU image is brand new and features Ubuntu 11.04. It has also a smaller disk of only 8GB compared to 15GB before. This helps to make it eligible for a free tier micro instance. Of course this instance type is not recommended for load testing, but you can easily test deployment and remote execution of XLT before you move up to more expensive setups.

Besides a few defect fixes, release 4.0.5 delivers four great improvements to speed up test case creation and maintenance with Script Developer and make your work more productive.

• The XLT Script Developer runs on Firefox 4 and 3 now.
• Test variables are now resolved recursively, so you can use variables within resolved content.
• There is no need to open modules anymore if you want to edit a line or two of it. Also enabling/disabling of module code can be done easily from the main test case. This saves time and aids script maintenance.
• During script debugging and script execution, you can now evaluate assertions instantly to see whether or not your verification expression will match.

The full set of release notes can be viewed directly in the release area. You will also find documentation and the download link there. As usual, th

HTTP-level tools record HTTP requests on the HTTP protocol level. They usually provide functionality for basic parsing of HTTP responses and building of new HTTP requests. Such tools may also offer parsing and extraction of HTML forms for easier access to form parameters, automatic replacement of session IDs by placeholders, automatic cookie handling, functions to parse and construct URLs, automatic image URL detection and image loading, and so on. Extraction of data and validation are often done with the help of string operations and regular expressions, operating on plain HTTP response data. Even if HTTP-level tools address many load testing needs, writing load test scripts using them can be difficult.

Challenges with HTTP-Level Scripting

Challenge 1: Continual Application Changes

Many of you probably know this situation: A load test needs to be prepared and executed during the final stage of software development. There is a certain time pressure, because the go-live date of the application is in the near future. Unfortunately, there are still some ongoing changes in the application, because software development and web page design are not completed yet.

Your only chance is to start scripting soon, but you find yourself struggling to keep up with application changes and adjusting the scripts. Some typical cases are described below.

• The protocol changes for a subset of URLs, for example, from HTTP to HTTPS. This could happen because a server certificate becomes available and the registration and checkout process of a web shop, as well as the corresponding static image URLs, are switched to HTTPS.
• The URL path changes due to renamed or added path components.
• The URL query string changes by renaming, adding or removing URL parameters.
• The host name changes for a subset of URLs. For example, additional host names may be introduced for a new group of servers that delivers static images or for the separation of content management URLs and application server URLs that deliver dynamically generated pages.
• HTML form parameter names or values are changed or form parameters are added or removed.
• Frames are introduced or the frame structure is changed.
• JavaScript code is changed, which leads to new or different HTTP requests, to different AJAX calls, or to a new DOM (Document Object Model) structure.

In most of these cases, HTTP-level load test scripts need to be adjusted. There is even a high risk that testers do not notice certain application changes, and although the scripts do not report any errors, they do not behave like the real application. This may have side effects that are hard to track down.

Challenge 2: Dynamic Data

Even if the application under test is stable and does not undergo further changes, there can be serious scripting challenges due to dynamic form data. This means that form field names and values can change with each request. One motivation to use such mechanisms is to prevent the web browser from recalling filled-in form values when the same form is loaded again. Instead of “creditcard_number”, for example, the form field might have a generated name like “cc_number_9827387189479843″, where the numeric part is changed every time the page is requested. Modern web applications also use dynamic form fields for protection against cross-site scripting attacks or to carry security-related tokens.

Another problem can be data that is dynamically changing, because it is maintained and updated as part of the daily business. If, for example, the application under test is an online store that uses search-engine-friendly URLs containing catalog and product names, these URLs can change quite often. Even worse, sometimes the URLs contain search-friendly catalog and product names, while embedded HTML form fields use internal IDs, so that there is no longer an obvious relation between them.

Session IDs in URLs or in form fields may also need special handling in HTTP-level scripts. The use of placeholders for session IDs is well supported by most load test tools. However, special script code might be needed, if the application not only passes these IDs in an unmodified form, but also uses client-side operations on them or inserts them into other form values.

To handle the above-mentioned cases, HTTP-level scripts need manually coded, and thus unfortunately also error-prone, logic.

Challenge 3: Modeling Client-Side Activity

In modern web applications, JavaScript is often used to assemble URLs, to process data, or to trigger requests. The resulting requests may also be recorded by HTTP-level tools, but if their URLs or form data change dynamically, the logic that builds them needs to be reproduced in the test scripts.

Besides this, it can be necessary to model periodic AJAX calls, for example to automatically refresh the content of a ticker that shows the latest news or stock quotes. For a realistic load simulation, this also needs to be simulated by the load test scripts.

Challenge 4: Client-Side Web Browser Behavior

For correct and realistic load simulations, the load test tool needs to implement further web browser features. Here are a few examples:

• Caching
• CSS handling
• HTTP redirect handling
• Parallel and configurable image loading
• Cookie handling

Many of these features are supported by load test tools, even if the tools act on the HTTP level, but not necessarily all of them are supported adequately. If, for example, the simulated think time between requests of a certain test case is varied, a low-level test script might always load the cacheable content in the same way – either it was recorded with an empty cache and the requests are fired, or the requests were not recorded and will never be issued.

DOM-Level Scripting

What is the difference between HTTP-level scripting tools and DOM-level scripting tools? The basic distinction between the levels is the degree to which the client application is simulated during the load test. This also affects the following characteristics:

• Representation of data: DOM-level tools use a DOM tree instead of simple data structures.
• Scripting API: The scripting API of DOM-level tools works on DOM elements instead of strings.
• Amount and quality of recorded or hard-coded data: There is much less URL and form data stored with the scripts. Most of this data is handled dynamically.

DOM-level tools add another layer of functionality on top. Besides the handling of HTTP, these tools also parse the contained HTML and CSS responses to build a DOM tree from this information, similar to a real web browser. The higher-level API enables the script creator to access elements in the DOM tree using XPath expressions, or to perform actions or validations on certain DOM elements. Some tools even incorporate a JavaScript engine that is able to execute JavaScript code during the load test.

Advantages

DOM-level scripting has a number of advantages:

• Load test scripts become much more stable against changes in the web application. Instead of storing hard-coded URLs or data, they operate dynamically on DOM elements like “the first URL below the element xyz” or “hit the button with id=xyz”. This is especially important as long as application development is still ongoing. As a consequence, you can start scripting earlier.
• Scripting is easier and faster, in particular if advanced script functionality is desired.
• Validation of result pages is also easier on the DOM level compared to low-level mechanisms like regular expressions. For example, checking a certain HTML structure or the content of an element, like “the third element in the list below the second H2” can be easily achieved by using an appropriate XPath to address the desired element.
• Application changes like changed form parameter names normally do not break the scripts, if the form parameters are not touched by the script. But, if such a change does break the script because the script uses the parameter explicitly, the error is immediately visible since accessing the DOM tree element will fail. The same is true for almost all kinds of application changes described above. Results are more reliable, because there are fewer hidden differences between the scripts and the real application.
• CSS is applied. Assume there is a CSS change such that a formerly visible UI element that can submit a URL becomes invisible now. A low-level script would not notice this change. It would still fire the old request and might also get a valid response from the server, in which case the mismatch between the script and the changed application could easily remain unnoticed. In contrast, a DOM-level script that tries to use this UI element would run into an error that is immediately visible to the tester.
• If the tool supports it, JavaScript can be executed. This avoids complicated and error-prone re-modeling of JavaScript behavior in the test scripts. JavaScript support has become more and more important in recent years with the evolution of Web 2.0/AJAX applications.

Disadvantages

There is one disadvantage of DOM-level scripting. The additional functionality needs more CPU and main memory, for instance to create and handle the DOM tree. Resource usage increases even more if JavaScript support is activated.

Detailed numbers vary considerably with the specific application and structure of the load test scripts. Therefore, the following numbers should be treated with caution. Table 1 shows a rough comparison, derived from different load testing projects for large-scale web applications. The simulated client think times between a received response and the next request were relatively short. Otherwise, significantly more users might have been simulated per CPU.

If you evaluate these numbers, please keep in mind that machines are becoming ever more powerful and that there are many flexible and easy-to-use on-demand cloud computing services today, so that resource usage should not prevent DOM-level scripting.

Conclusion

Avoid hard-coded or recorded URLs, parameter names and parameter values as far as possible. Handle everything dynamically. This is what we have learned. One good solution to achieve this is to do your scripting on the DOM level, not on the HTTP level. If working on the DOM level and/or JavaScript execution are not possible for some reason, you always have to make compromises and accept a number of disadvantages.

We have created and executed web-application load tests for many years now, in a considerable number of different projects. Since 2005, we have mainly used our own tool, Xceptance LoadTest (XLT), which is capable of working on different levels and supports fine-grained control over options like JavaScript execution. In our experience, the advantages of working on the DOM level, in many cases even with JavaScript execution enabled, generally by far outweigh the disadvantages. Working on the DOM level makes scripting much easier and faster, the scripts handle many of the dynamically changing data automatically, and the scripts become much more stable against typical changes in the web application.

Ronny Vogel is technical manager and co-founder of Xceptance. His main areas of expertise are test management, functional testing and load testing of web applications in the field of e-commerce and telecommunications. He holds a Masters degree (Dipl.-Inf.) in computer science from the Chemnitz University of Technology and has 16 years of experience in the field of software testing. Xceptance is a provider of consulting services and tools in the area of software quality assurance, with headquarters in Jena, Germany and a branch office in Cambridge, Massachusetts, USA.

As always, updates are free for all customers and all people using XLT despite the license.

An update of the AWS cloud images will follow in the next hours.

Most modern programming languages are virtual machine based and these machines have knobs you can turn to adjust their behavior according to your requirements. XLT runs on Java and so all the things you might have already learnt from tuning your Java-based servers apply to XLT as well. If you do not have experience in tuning your Java-based servers, you will learn a lot that can be applied to your servers and help you to increase performance.

So, let’s take a look at the upcoming XLT feature that provides you with more details about garbage collection (GC) without the need to use any external tool to monitor or analyze logs or JVMs runtime behavior.

Perfect GC behavior

This is a chart displays nice memory statistics that indicate absolutely no problems with the garbage collection. As you can see the memory usage (first chart in the image) is alternating but never touching the upper limit. The second chart gives you the times when full garbage collection occurred, basically these are the bad events. Events that block the virtual machine from continuing to run. We should avoid these at any cost… nearly, because a full GC is costly. There was only one full GC right at the beginning at the test. This is a normal JVM behavior. So we seem to have done a pretty good job. No major collection of garbage. Sweat!

There are still the minor collections. Minor collections occur frequently and they reclaim small portions of memory with short living objects. The third charts shows us, that minor collection took about 10 to 30 ms, some spikes up to 70 ms. This is acceptable.

GC with Issues

Ok, let’s have a bad example in comparison. It runs with almost default VM settings. This means just min and max heap were set (Xms256MB/Xmx512MB). You can see clearly that a lot of major collections were running for up to 800 ms each. Also the minor collections were longer.

Clearly, the new charts help you see and fix misbehavior quickly. “What about the settings?” you might ask now. Yes, this example is not very helpful without revealing the difference between both test runs. So, we will give you the settings of the good one. The bad run had only Xms and Xmx set, as mentioned before.

## Set minimum memory to use
-Xms512m

## Set maximum permitted memory
-Xmx512m

## Enable concurrent old GC to avoid sudden long pauses
-XX:+UseConcMarkSweepGC

## When to start GC for the tenured/old area of the memory.
## This has to be low enough to avoid that threads need
## memory and can not get any before the GC has finished.
## This will lower the wait time.
-XX:CMSInitiatingOccupancyFraction=70

That’s really all. The use of the Concurrent-Mark-Sweep-Collector (CMS) is the most important setting. The CMS does not block the main VM worker threads, but collects the garbage concurrently. Because there might be situations were the CMS collector is not fast enough in cleaning up, this means the old space runs out of free memory, we give the CMS a hint with the last line. This line explicitly tells the CMS to start early with the clean up. In this case at a 70% fill level. The default is 96% and way too high.

One last thing. Setting Xms and Xmx to the same number helps the VM to relax because it will not try to get back to the minimal memory limit (Xms) and so it cleans less aggressively.

If you want to lean more about Java Garbage Collection, take a look at this Oracle documents: GC Tuning.

You might be especially interested in the new Script Developer. Our main feature of XLT 4.0.

The script developer is our approach to write and execute scripts efficiently within Firefox. It is a tool to quickly automate web application, share scripts without the hassle of complicated installations, while maintaining full control over possible other ways to execute scripts. The script developer lays the foundation to run test within the browser, execute scripts during builds, create and run test-driven tests, and, if required, export scripts into Java to unleash the power of a modern programming language.

Enjoy the screencasts and of course feedback is always welcome.

• EU-West: ami-9b5064ef
• US-East: ami-5647b63f
• US-West: ami-539dcd16

The usage of the images is free or charge but you have to pay your AWS usage costs of course. Please keep in mind that you need a valid license to run a load test with more than 5 virtual users.

Script Developer

As an alternative to writing test cases in Java, you can now use the XLT Script Developer to create script test cases. Script test cases are based on a simple syntax and a reduced set of operations, which makes them a perfect fit for non-programmers. Only the Script Developer, which is an extension to Firefox, is necessary to create, edit, and manage basic script test cases.

To create a new script test case, the test designer simply uses the application under test. All interactions with the application are recorded in the background and stored to an XML script file as a sequence of script commands. While recording, assertion commands to validate the web pages may be inserted manually. From the Script Developer, script test cases can be replayed in Firefox at any time to quickly check whether the test case still runs successfully.

Existing script test cases can be modified later on, for example, to add new or delete obsolete commands. Common command sequences, which could be reused in other test cases as well, can be refactored to parameterizable script modules. Finally, any recorded value can be extracted out of the script into a test data file to separate test data from script code.

Script files can also be run outside of the browser, via the XLT framework, which simulates a head-less browser. This mode is suitable for unattended test case execution, during functional or load tests. When saving scripts, the Script Developer also creates JUnit test case classes as “wrappers” around script test cases, which serve as a bridge between the XLT framework and the script world. This way, from the framework’s point of view, script test cases are in no way different from test cases written in Java.

More Data to Query

For improved tests accuracy, you can now query the request and response data and run assertions on it. This permits checks on the communication because not all requests are reflected in the DOM tree.

Improved EC2 Handling

AWS (Amazon Web Services) added the ability to tag EC2 resources to simplify the administration of your cloud infrastructure. As a form of meta data, tags can be used to create user-friendly names and improve coordination between multiple users. The XLT EC2 administration tool ec2_admin features an additional menu which lets you select your EC2 resources based on the tag name.

Better Automation

To improve automation of tests, we added the ability to pass properties on the mastercontroller command line. Additionally the test definition file for the test suite can be redefined on the command line as well.

Faster Work Flow

When test goes wrong or a logging is turn up, the data to download from all agents can be pretty big. To get a fast or selective result, you can now decide how much data you want to download.

JDK Compatibility

Beginning with v4.0, XLT requires a Java virtual machine 6 or above to run. Java 5 is not supported any longer. The reason is the end-of-life announcement for JDK 5.

Misc

We refreshed HtmlUnit and updated it to version 2.8, Ruby got updated to 1.5.1, and WebDriver is now v2.0a6. The event API got simplified and is now easier to use.

Where to get it

More information about the release, the quick start guide, and the manual can be found in the release area. Of course, the full download of XLT 4.0 is available there too. 

We are looking forward to your feedback, comments, and of course… Happy testing!

A short ramp up period in the beginning of the test and afterwards we kept a steady load factor. For the steady phase we reached more than 11,000 hits per second.

The target system was seeing about 2,200 concurrent users during the peak of the test.

During that test, the network was transporting about 95 Mbytes/s inbound traffic, this is a network utilization of about 760 Mbit/s. Amazing that the EC2 boxes in the EU data center can handle that traffic. We used just 10 boxes and each box has a 100Mbit network, so the overall limit must have been reached we think.

By the way, the target system recovered easily and was able to serve its normal duties without any problems. But this test clearly showed the limits in terms of throughput. But this test did not show any limits of XLT 4.0, because neither the load boxes in terms of CPU nor the reporting had any problems with this test size.

Customers of XLT can access all information regarding this release at the Xceptance Information Center. This release is also publicly available for download.

Das soll mir Bob Ross erstmal nachmachen.

Warum geht es im Allgemeinen?

Visits und Sessions sind Begriffe aus der Webentwicklung, werden aber auch als Metriken im Webumfeld genutzt. Der technische Teil verbindet sich in der endgültigen Definition mit der wirtschaftlich/mathematischen zur eigentliche Bedeutung. Was wir also wollen ist: a) wissen was dahinter steckt, b) erfahren was die Begriffe definieren und c) wissen wozu man die Zahlen braucht.

Was ist ein Visit?

Wenn man sich dazu entschließt, eine Webseite zu besuchen, dann ruft man irgendwann eine erste Seite auf. In diesem Moment hat man einen Visit begonnen oder auf Deutsch – man ist zum Besucher geworden. So lange man sein Surfen auf dieser Webseite fortsetzt, solange setzt man seinen Visit fort. Alle einzelnen Seiten zusammengenommen, bilden damit, beginnnend mit der ersten Seite, einen Visit.

Für den Betreiber ist damit klar, dass ein Interessent oder Kunde seiner Webseite einen Besuch abgestattet hat. Am besten läßt sich das mit dem Besuch eines realen Ladens vergleichen. Wenn man in den Laden geht, dann beginnt man seinen Besuch/Visit und wenn man ihn wieder verlässt, dann endet der Besuch/Visit.

Natürlich gibt es auch Ausnahmen von der Regel. Wenn man nur mal schnell 5 Minuten in die Küche geht bzw. in einem realen Laden schnell zum Auto läuft, weil man sein Geld vergessen hat, dann zählt das nur als ein Visit, weil man nur eine Besuchsabsicht hatte.

Über die Metrik Visit läßt sich damit einfach messen, wieviele Besuchsabsichten pro Zeiteinheit vorgelegen haben und auch in die Tat umgesetzt wurden. Dabei spielt es keine Rolle, ob man etwas kauft, zurückbringt oder gleich wieder an der Tür kehrt macht.

Im Internet gibt es nicht nur echte Besucher, sondern auch jede Menge Automaten, die sich in den Netzweiten herumtreiben und mit jedem Abruf einer oder mehrerer Seite jeweils auch einen Visit erzeugen. Das bringt natürlich die Statistiken durcheinander. Deshalb versucht man durch technische Maßnahmen, diese meist unrelevanten Besuche herauszurechnen. Das Wie kann bei Interesse ein weiterer Blogeintrag werden.

Was ist eine Session?

Nun haben wir geklärt, was hinter dem Begriff Visit steckt, aber was ist dann eine Session?

Einfach gesagt, ist eine Session die technische Abbildung eines Besuchs/Visit. Die genutzte Technik und Software müssen sich nämlich merken, welche Anfragen zusammengehören, damit es möglich wird, Dinge wie ein Login oder einen Warenkorb technisch umzusetzen.

Sessions bestehen aus Daten, die Informationen über die Vorgänge des Visits zusammenfassen, oft als Sessioninformationen bezeichnet. Diese Datensätze haben im Regelfall eine begrenzte Lebenszeit. Wenn man seinen Visit beendet bzw. nicht fortsetzt, also nicht mehr klickt, dann beginnt eine Uhr zu ticken, die nach eine einstellbaren Zeit (oft 30 Minuten bis 2 Stunden), die Daten entfernt, damit es zu keinen Überläufen kommt. Das nennt sich Session-Timeout. Nimmt man vor Ablauf der Zeit seinen Besuch wieder auf, kommt also in den Laden zurück, dann beginnt die Uhr von Neuem zu ticken.

Vergleichbar ist es mit der Situation, dass man an der Kasse sein Geld nicht findet, den Korb schnell an der Kasse lässt, um Geld zu holen. Kommt man nun nicht rechtzeitig zurück, dann hat jemand den Korb ausgeräumt und die Waren zurückgestellt.

Die Anzahl der Sessions müsste eigentlich immer gleich der Anzahl der Visits sein. Da aber Visits oft anders gezählt werden, weil geschäftliche Kriterien dahinter stehen und keine technischen, liegen oft die Visits unter der Anzahl der Sessions pro Zeiteinheit.

Wir hoffen, dass diese kurze Erklärung hilft, die Begriffe Visit und Session zu verstehen und auseinander zu halten.

Dahinter verbirgt sich schon die erste Neuerung, denn mit dem Download besitzt man automatisch eine freie Basislizenz. Sie erlaubt Tests mit bis zu fünf virtuellen Nutzern, gilt zeitlich unbegrenzt und unterliegt keinen Nutzungseinschränkungen. Damit darf man XLT auch kommerziell einsetzen, beispielsweise intern oder in Kundenprojekten. So kann man ungehindert prüfen, ob XLT das Werkzeug der Wahl ist oder man kann XLT bereits produktiv für Regressionstests verwenden.

XLT 3.3 bietet einige neue Features, die die tägliche Arbeit effizienter gestalten und den Einsatzbereich von XLT erweitern:

• Comparison-Reports zum detaillierten Vergleich zweier Testläufe
• Trend-Reports zur Visualisierung von Veränderungen in den Testergebnissen über mehrere Testläufe hinweg
• Unterstützung des Google WebDriver API für schnelles Prototyping von Testfällen
• Ruby als zusätzliche Scriptsprache zur Testfallerstellung
• Programmierbeispiele für typische Anwendungsfälle, zum Beispiel für die Bearbeitung von Ajax-Requests und die Behandlung von Popups oder Frames
• Überarbeiteter Testrecorder mit der Unterstützung für Voreinstellungen zur Codegenerierung

Zusätzlich sind wieder viele Detailverbesserungen in diese Version eingeflossen. Weiterführende Informationen gibt es in den Releasenotes oder auf den Produktseiten unseres Webauftritts.

Der Script-Recorder ist für Firefox 3 und 3.5 geschrieben und funktioniert auf allen populären von Firefox unterstützten Plattformen. Selbst getestet haben wir die Kombination mit Microsoft Windows XP und Vista, Linux Ubuntu und Fedora, sowie MacOS X.