How to create clone test instance from production site?

I want to create a copy of my production site as testing site. Please suggest a method to copy the same database and link it to new site for testing.

Just use bench --site SITENAME backup and find the backup in sites/SITENAME/private/backups. Then mount it in the database of your test site with bench --site TESTSITENAME --force restore PATH_TO_BACKUP_FILE