fix

Now, run_tests for -l option pass

Memo: Rake's bad behavior

1 -> 2
3 -> 2
4 -> 1
4 -> 3

then run 4 -> run 2, 1, 3
(does not run 2 twice!!! really confusing)

Signed-off-by: Akira Hayakawa <ruby.wktk@gmail.com>