How do I run make Jenkins run my tests prior to building my OpenShift node.js app?

I've a got a simple node app that deploys successfully using the Jenkins cartridge at OpenShift. I have karma tests I'd like to run prior to kicking off the build stage. Test failures should cause the build to fail.

I think I need define a pre_build action_hook, but I cannot find any examples of running tests. Can someone give me a example of action_hook file that will run my tests?

Thanks in advance.