Presently, all the tests in java/time inherit all dependencies from the test library by declaring the library with the lib.dirs property:
java/time/TEST.properties:lib.dirs = ../../lib/testlibrary

The lib.dirs property is compiling the directories recursively, hence all dependencies of the test library and all the sub-directories in it are inherited.

Possibly, a fix in JTReg is also required to allow compilation of selected subdirectories.