/usr/lib/mysql-testsuite/t/init_file-master.opt is in percona-server-test-5.6 5.6.22-rel71.0-0ubuntu4.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 | --init-file=$MYSQL_TEST_DIR/std_data/init_file.dat
|