jtreg doesn't depend on a Java runtime because it can use the JDK being
tested to run. This is done by setting the JT_JAVA environment variable
(or JAVA_HOME with jtreg 4.1-2 in Wheezy).
The best we could do would be to add a suggested dependency, but this
can't be a hard dependency.
Also note that you'll have to backport jtreg 4.1-b09-1 from unstable if
you want to run the openjdk-8 tests in Wheezy, jtreg 4.1-2 doesn't work.
This is the maintainer address of Debian's Java team
debian-j...@lists.debian.org for discussions and questions.