/usr/share/ant/lib/ant-junit.jar is in ant-optional 1.8.2-4build1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/ant/lib/../../java/ant-junit-1.8.2.jar
/usr/share/ant/lib/../../java/ant-junit-1.8.2.jar