The tests for jtreg itself are currently spread across up to 3 locations

make/tests/*.gmk for the makefile
src/share/test/javatest/regtest/*.java for standalone tests
src/share/test/javatest/regtest/data/* for test suites for tests
 
(and the guidelines are not followed 100%)

It would be better to rationalize the layout, so that each test is represented by a file or directory in test/. As a special case, the "basic" test suite which is used by a number of tests could be put in test/share.