Client::getUUID() is used in auditing to uniquely identify a single logical connection.  By making it introspectible from an active client, it will facilitate identifying audit log messages from actions taken by a jstest execution.

const myUUID = conn.adminCommand({connectionStatus: 1}).uuid;
conn.getDB('admin').auth('user', 'pwd');
audit.assertEntry({atype: 'authenticate', uuid: myUUID});

This will reduce the noise caused by false-positives/false-negatives from background cluster activity during tests.