/usr/lib/x86_64-linux-gnu/libXtst.so.6 is in libxtst6 2:1.2.0-4ubuntu0.1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libXtst.so.6.1.0
/usr/lib/x86_64-linux-gnu/libXtst.so.6.1.0