/usr/lib/mysql-testsuite/t/mysql_protocols.test 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 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | # Embedded server doesn't support external clients
--source include/not_embedded.inc
# Windows does not have SOCKET, but will try to create a PIPE as well as MEMORY
--source include/not_windows.inc
# test for Bug #4998 "--protocol doesn't reject bad values"
--exec echo "select ' ok' as '<default>'" | $MYSQL
--exec echo "select ' ok' as 'TCP'"       | $MYSQL --protocol=TCP
--exec echo "select ' ok' as 'SOCKET'"    | $MYSQL --protocol=SOCKET
--exec echo "select ' ok' as 'PIPE'"      | $MYSQL --protocol=PIPE    2>&1 || true
--exec echo "select ' ok' as 'MEMORY'"    | $MYSQL --protocol=MEMORY  2>&1 || true
--exec echo "select ' ok' as 'NullS'"     | $MYSQL --protocol=NullS   2>&1 || true
# End of 4.1 tests
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