For my new project Xapper I decided to try and write my tests in Groovy. Previously I had used Groovy scripts to generate data for Java tests but I was curious as to whether it would be easier to write the entire test in Groovy instead of Java.

Overall the experience was a qualified “yes”. When I was initially working with the tests it was possible to invoke them within Eclipse via the GUnit Runner. Trying again with the more recent 1.5.7 plugin, the runner now seems to be the JUnit4 one and it says that it sees no tests, to paraphrase a famous admiral. Without being able to use the runner I ended up running the entire suite via Gant, which was less than ideal, because there is a certain amount of spin-up time compared to using something like RSpec’s spec runner.

I would really like all the major IDEs to get smarter about mixing different languages in the same project. At the moment I think Eclipse is the closest to getting this to work. NetBeans and Intellij have good stories around this but it seems to me to be a real pain to get it working in practice. I want to be able to use Groovy and Java in the same project without having Groovy classes be one of the “final products”. NetBeans use of pre-canned Ant files to build projects is a real pain here.

Despite the pain of running them though I think writing the tests in Groovy is a fantastic idea. It really brought it home to me, how much ceremony there is in conventional Java unit test writing. I felt like my tests improved when I could forget about the type of a result and just assert things about the result.

Since I tend to do TDD it was great to have the test run without having to satisfy the compiler’s demand that methods and classes be there. Instead I was able to work in a Ruby style of backfilling code to satisfy the runtime errors. Now some may regard this a ridiculous technique but it really does allow you to provide a minimum of code to meet the requirement and it does give you the sense that you are making progress as one error after another is squashed.

So why use Groovy rather than JRuby and RSpec (the world’s most enjoyable specification framework)? Well the answer lies in the fact that Groovy is really meant to work with Java. Ruby is a great language and JRuby is a great implementation but Groovy does a better job of dealing with things like annotations and making the most of your existing test libraries.

You also don’t have the same issue of context-switching between different languages. Both Groovy and Scala are similar enough to Java that you can work with them and Java without losing your flow. In Ruby, even simple things like puts versus println can throw you off. Groovy was created to do exactly this kind of job.

If the IDE integration can be sorted out then I don’t see any reason why we should write tests in Java anymore.