Historically, RHQ has had a little bit of a problem with test coverage of its various (agent) plugins. There is a multitude of problems with testing these but the following two are, IMHO, the main ones:
You somehow need to have the managed resource available for the plugin to connect to (i.e. you need to have the JBoss AS, Postgres or whatever your plugin manages). This is always a problem for a clean quick unit test. You either somehow need to mock the managed resource (try that with Postgres) or you need to have a way of configuring your test to get at or start the managed resource. This is where Arquillian certainly can come to the rescue with its ability to manage the lifecycle of its “containers” (for managed resources that have an Arquillian extension, like JBoss AS) but generally this needs to be in the “hands” of the tests for each plugin. There are a million ways the plugins talk to their managed resources and so trying to come up with a generic solution to start, stop and configure them would IMHO create more problems than it would solve.
Setting up Agent Environment
While not even too hard, running your test in RHQ’s plugin container requires a little bit of setup. It is important to realize that if you want your tests to be run inside a real plugin container (i.e. “almost an RHQ agent”), it is not enough to have your dependencies on your test classpath. The thing is that the plugin container is a container of its own – it has its own deployment requirements and classloading policies. It is best to think about deploying a plugin into RHQ agent as deploying a webapp into Tomcat – you wouldn’t expect to be able to test the webapp in Tomcat just by virtue of having them both on the classpath and starting Tomcat.
So to put it straight, you need to jump through some maven and antrun hoops to package your plugin (and any other plugin it depends on) and put them in defined locations, where the plugin container can then pick them from. Also, if you want to take advantage of our native APIs to obtain running processes, etc., you need to use another bucket of
antrun incantations in your POM to set that up.
The two problems outlined above caused that the test coverage of our plugins is rather low. We always knew this sucked and there have been attempts to change that.
ComponentTest class used in some of our plugins is an attempt at testing the plugins out-of-container, bootstrapping them with some required input. Advantage of this approach is that you don’t need to care about the plugin container and its intricacies, disadvantage being that you don’t get to test your plugin in an environment it will be deployed to. Also, you need to implement support for bootstrapping the parameters for any plugin facet your plugin implements – in the end you’d end up reimplementing large parts of the plugin container just for the testing needs.
Another attempt was the
@PluginContainerSetup annotation that took care of the configuration and lifecycle of the plugin container. The advantage was that you got access to a real plugin container running with your plugins, disadvantage being that you still were required to perform some maven and antrun artistry so that the plugin container could find all the plugins and libraries you’d need.
As I already hinted at above, the RHQ agent shares a lot of similarities with EE/Servlet containers from the deployment point of view. Arquillian was therefore an obvious choice to try and solve our plugin test problems once and for all (well, this is a lie – the problem with having to have a managed resource available for the test is a problem that cannot be reasonably solved using a single solution).
So what is this integration about? It certainly won’t help you, as the plugin developer, with connecting to a managed resource you’re creating your plugin for. But it does bring you a lot of convenience over the previous state of things if you want to test your plugin in container.
Most importantly there is no more any maven and/or antrun required to test your plugin in-container. You just define your plugin in the Arquillian way using the
@Deployment annotation (and you can “attach” to it any another plugins it depends on by instructing Arquillian to use the maven resolver). Using
arquillian.xml (yes, a configuration file but an order of magnitude shorter and much more focused and simple than
pom.xml), you can configure your container to use RHQ’s native APIs by flipping one config property to true. You can declaratively say you want to run discovery of managed resources (using, surprise, a
@RunDiscovery annotation) and you get get results of such discovery injected into a field in your test class. You can even set the container up so that it thinks it is connected to an RHQ server and you can provide your
ServerServices implementation (i.e. the RHQ server facade interface) and there is a default implementation ready that uses Mockito to mock your serverside. There’s still more, you can read all about the supported features and see some examples on this wiki page.
While not a panacea for all problems the testing of RHQ plugins brings about, using Arquillian we were able to cut the setup needed to run a plugin in-container by 90% and we were able to introduce a number of convenience annotations using which you can get a variety of data injected into your unit tests. This is still just a beginning though, the next step is to start actually using this integration and come up with other useful annotation and/or helper methods/classes that will ease the working with and retrieving information from the plugin container as much as possible.