Concordion itself is a test framework which runs your executable specifications using test fixtures.
The executable specifications are written in HTML and are independent of any programming language. The same executable specifications can be used with Concordion for Java, or Concordion.NET. (and a subset of the syntax can be used with the Ruby and Python ports of Concordion).
The test fixtures are written in a programming language. For the Java version of Concordion, the test fixtures are written as JUnit classes. (However they don't include test methods and don't tend to include assertions, since these are defined in the executable specification.)
There are 2 main ways in which Concordion is used. Either through the User Interface, or "under the covers" to the application or services layer.
When testing "under the covers" of the application, the test fixture calls into the application code directly. In this case, the type of application is largely irrelevant.
When testing through the user interface, you need a Test Driver. Test drivers provide the functionality to find widgets, click buttons, enter text etc. There are a lot of high quality, open source test drivers available. Some of these, such as Selenium and SoapUI also come with their own test frameworks, but can be used purely as test drivers. The test drivers I have used with Concordion are:
|Application Type||Test Driver|
|Web Application||WebDriver and Selenium|
|Swing GUI Application||Fest|
Additionally there are a lot of test extension libraries available, such as DbUnit and XmlUnit that can be called from your test fixture.
Concordion is a great framework for running your executable specifications. When combined with the right driver you can test pretty much any type of application.