Grails skipping unit tests

Every now and then the Grails (2) framework surprises me. Sometimes in a good way, and sometimes in the worst possible way.

It turns out that when the path your Grails project is in contains a percentage sign, the build does not work correctly. I've seen two effects (depending on various settings):

1. Grails starts, but the compilation of plugin classes fails (classes not found)
2. Grails starts, compiles, starts testing, but then does not actually run any tests.

The really annoying part in this is that there is no error message, no build failure, no warnings. Just silence, and unit tests are not being run. Sigh.

The Grails build system (not Gradle) does not handle paths very well. Always make sure that the path to your project is 'simple'. This means no funny characters and staying clear of common grails artifact names (and possibly even 'conceptual' names).