basically the setup is https://github.com/jruby/jruby/blob/master/maven/jruby/src/it/runnable

just exchange "-T" with spec in this line
https://github.com/jruby/jruby/blob/master/maven/jruby/src/it/runnable/pom.xml#L200

this fails first because of #2968 and secondly the current working directory is "uri:classloader://" which the shell spawner can not change the directory to.

maybe it is feasible to use -C uri:classloader:// on the jruby executable in case both condition apply:

• executable is jruby
• PWD is uri:classloader://

that is the relevant error message from the above modified test:

[INFO] uri:classloader:/META-INF/jruby.home/bin/jruby -S rspec ./spec/one_spec.rb
[INFO] sh: 1: cd: can't cd to uri:classloader://
[INFO] sh: 1: uri:classloader:/META-INF/jruby.home/bin/jruby: not found
[INFO] uri:classloader:/META-INF/jruby.home/bin/jruby -S rspec ./spec/one_spec.rb failed