Currently, the only way I know to specify the system properties of the JVM used in the 'test' task is:

  test {
      options.fork( jvmArgs: [ "-Dfoobar=moo",  "-Dugly=duckling" ] )
  }

That is rather ugly for something you need to do fairly often.

What about something like:

test {
     systemProperties = [  foobar : "moo",     ugly: "duckling" ]
}

Or perhaps:

test {
    jvmArgs = [   "-Dfoobar=moo" , "-Dugly=duckling" ]
}

It would also be nice if the userguide discussed system properties of the
JVM that runs test when it's discussing setting system properties for the
build's JVM; this would help to underscore the difference.