Dean Wampler's Blog

I just released v0.7.0 of Contract4J5. This release adds support for using Groovy or JRuby instead of Jexl as the scripting engine for the test scripts embedded in annotations. In fact, Groovy is now the default.

The advantage of Groovy or JRuby is that they provide a richer environment for more sophisticated testing. They are also better suited for planned, long-term enhancements of Contract4J5 to support user-configurable annotations and behaviors, which will take the tool beyond Design by Contract support.

The only major disadvantage over Jexl is lower performance. I'll blog about those results next. You can also find details in the README.

I was pleased to find that all but a few of the existing Jexl-based unit tests worked without modification for Groovy. With a few hacks, I got them to work for JRuby as well. The differences for Groovy include slight differences in how Goovy vs. Jexl handle protected access (private, protected, etc.). Also, Groovy does not force you to provide a public accessor to evaluate tests on member fields, which Jexl required.

For JRuby, I found that almost all Ruby vs. Java differences could be handled if I did a few simple replacements of the most common Java idioms in scripts with the corresponding Ruby idioms:

• Replace equals(...) with eql?(...)
• Replace compareTo(...) with <=>(...)
• Replace null with nil

That is, Contract4J5, when using JRuby, will make these substitutions in your test expressions so they work, most of the time, even though they are written in Java syntax. This tends to work because the test expressions tend to be relatively simple and they often consist of comparisons to null or calls to String comparison methods.