Automatically testing advanced web applications (revisited)

More than one and a half years ago I first posted a blog article 'high automatic test coverage of web applications'. While working with this and later projects I realized that in order to have complete coverage and a more dynamic testing environment I had to take it a step further and therefore started inventing my own test framework, described in the article 'full testing with javascript'.

Soon thereafter I discovered the Selenium Core framework which was still rather immature. Since it functions similar to the framework I was working on, I gave it a go and never looked back.

Testing priorities in a web application
When testing you have to first plan what areas need the most testing. Test driven development requires a lot of focus on unit testing and functional testing. I will not discuss unit testing here, since it depends heavily on the platform of the web application.
Aside from unit testing, functional testing is the most important testing for web applications, because it can be used to directly measure progress and prohibits regression.
On a second place comes integration testing, because alot of problems tend to occur in communication with other systems.
In third comes performance testing. This tends to be the focus of automatic tests, but that is an ancient view imo. Performance testing is important, but it's rather easy once functional testing has been done, because you can leverage the functional tests and scale them to performance tests.
On a fourth place comes installation testing. Redeploying a web application is important, both for testing environments, but also for reestablishing an environment.

Functional testing
this is exactly what Selenium is for. It's fast and works for Python, Java and several other popular platforms. I would go for Python because the interactive compiler is killer for writing test cases. Java is not a bad alternative with Seleniums excellent integration with JUnit.
You should not need any other tool for this task.

Performance testing
For performance testing you could use HTTPUnit, which also integrates well with JUnit. It's a rather simple, but powerful framework for controlling all parameters of requests and monitoring the responses.
Functional test cases written for functional testing using Selenium could be rewritten easily and scaled to do performance testing.

Integration testing
This depends on what technology is used for communication, I'll only present the most common one here. Integration in web applications are typically over Web Services, therefore testing could be done with a framework for easily creating web clients, like Axis 2 and using JUnit to execute it, but HTTPUnit is also viable.

Installation testing
Installation testing involves two parts. Scripts to deploy the application and verification of the function.
Scripts would typically depend on the platform of the web application. For WebLogic or WebSphere, you would use ant targets available from the vendor. How you manage to deploy the application automatically is rather irrelevant, since you needn't verify anything during the process.
The second part of verifying function after installation is rather easy, since it's just a matter of running the functional tests.

Conclusion
Using a few open source tools is an easy, fast and effective way to test advanced Web Applications with lots of javascript and complexity.
Standardizing the executing can be achieved using a common executing framework like JUnit.