After a little hackage I have taken Eric Wendelin's suggestion and gone with Gradle.
To do this I have moved my groovy unit tests into the requisite directory structure src/test/groovy/, with the supporting resources (input and expected output XML files) going into the /src/test/resources/ directory.
All required libraries have been configured in the build.gradle file, as described (in its entirety) here:
apply plugin: 'groovy'
repositories {
mavenCentral()
}
dependencies {
testCompile group: 'junit', name: 'junit', version: '4.+'
groovy module('org.codehaus.groovy:groovy:1.8.2') {
dependency('asm:asm:3.3.1')
dependency('antlr:antlr:2.7.7')
dependency('xmlunit:xmlunit:1.3')
dependency('xalan:serializer:2.7.1')
dependency('xalan:xalan:2.7.1')
dependency('org.bluestemsoftware.open.maven.tparty:xerces-impl:2.9.0')
dependency('xml-apis:xml-apis:2.0.2')
}
}
test {
jvmArgs '-Xms64m', '-Xmx512m', '-XX:MaxPermSize=128m'
testLogging.showStandardStreams = true //not sure about this one, was in official user guide
outputs.upToDateWhen { false } //makes it run every time even when Gradle thinks it is "Up-To-Date"
}
This applies the Groovy plugin, sets up to use maven to grab the specified dependencies and then adds some extra values to the built-in "test" task.
One extra thing in there is the last line which makes Gradle run all of my tests every time and not just the ones it thinks are new/changed, this makes Jenkins play nicely.
I also created a gradle.properties file to get through the corporate proxy/firewall etc:
systemProp.http.proxyHost=10.xxx.xxx.xxx
systemProp.http.proxyPort=8080
systemProp.http.proxyUser=username
systemProp.http.proxyPassword=passwd
With this, I've created a 'free-style' project in Jenkins that polls our Mercurial repo periodically and whenever anyone commits an updated XSL to the repo all the tests will be run.
One of my original goals was being able to produce the standard Jenkins/Hudson pass/fail graphics and the JUnit reports, which is a success: Pass/Fail with JUnit Reports.
I hope this helps someone else with similar requirements.