The obvious use for jtreg -listtests is to create a list of tests to pass to jtreg later. But the stdout might contain unhelpful extra information like:

Directory "JTwork" not found: creating
Testsuite: ...

that has to be filtered out somehow. One obvious way is grep -v " " but of course that is errorprone.

Who is careful enough to filter out the exact string
Directory "JTwork" not found: creating
and '^Testsuite: '
?