While working with Nashorn sources I found it beneficial to execute a single test rather than all of them. With attached patch I can:
$ jdk8/nashorn/make$ ant test -
The patch changes the way list of test classes is composed. If the test.class property is specified, it is used, rather than including all the tests in the repository.
The patch also includes changes to nashorn/make/nbproject/*xml files to make sure the Ant task can be used from the NetBeans IDE. After opening the nashorn/make project, one can choose a test file, right click and either "Run Test" or "Debug Test".