How do I make Jenkins build fail when Maven unit tests fail?

You can add -Dmaven.test.failure.ignore=false to the MAVEN_OPTS if you click on Advanced button in the Build section of your Jenkins Job.

See Maven Surefire Plugin - surefire:test options for reference.

Use Text Finder plugin. Configure it to look for There are test failures and downgrade the build to FAILED

Another hack that can be useful is to use groovy post-build to check and set test result.

e.g. this groovy gets build result, appends useful things to build description and sets build result to UNSTABLE in the case that there are no pass or fail but all tests skipped.

def currentBuild = Thread.currentThread().executable// must be run groovy post-build action AFTER harvest junit xml  if you use junit xml test resultstestResult1 = currentBuild.testResultActioncurrentBuild.setDescription(currentBuild.getDescription() + "\n pass:"+testResult1.result.passCount.toString()+", fail:"+testResult1.result.failCount.toString()+", skip:"+testResult1.result.skipCount.toString())// if no pass, no fail all skip then set result to unstableif (testResult1.result.passCount == 0 && testResult1.result.failCount == 0 && testResult1.result.skipCount > 0) {   currentBuild.result = hudson.model.Result.UNSTABLE}currentBuild.setDescription(currentBuild.getDescription() + "\n" + currentBuild.result.toString())def ws = manager.build.workspace.getRemote()myFile = new File(ws + "/VERSION.txt")desc = myFile.readLines()currentBuild.setDescription(currentBuild.getDescription() + "\n" + desc)