https://discuss.asciidoctor.org/Latest-version-of-Asciidoctor-does-not-integrate-with-AJI-project-tp366p367.html
Alex,
First, great news! Continuous integration FTW!
I did a brief exploration on my box (since I wanted to become familiar with the CI build anyway) and what I noticed is that this is an issue with the setup script. I recently changed the Asciidoctor version from 0.1.4.pre to 0.1.4.preview.1 [1]. That seems to be causing a problem with how JRuby resolves the gem under target/classes.
To be honest, I'm not sure I understand how it worked before. Instead of trying to overlay Asciidoctor HEAD onto version 0.1.3 to trick JRuby into using the right code base, I think the script should be installing the unreleased version of Asciidoctor into the local Maven repository and then building against a real gem. This is not only simpler, but it also makes the results more accurate.
I've put together a pull request that switches to this strategy. It's necessary to install the gem outside of the Maven lifecycle because, well, Maven just isn't that smart. Thus, Travis will invoke a shell script instead of mvn directly.
-Dan
Btw, I noticed that you are only running CI against the unreleased version of Asciidoctor. I think you should include building against the current released version in the build matrix. Travis supports running multiple builds (or you could just run mvn twice inside the test-asciidoctor-master.sh).