Marking the test iterations as subtests means that when one fails, it
can identify clearly which iteration has failed.
(Bitbake rev: 52c55e681332d7cdbe06f3c9d9c8d77cb0cb93f6)
Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>