High end networked-systems have quickly climbed from a throughput of gigabits/sec to terabits/sec, and are approaching petabits/sec. Alas, network testing equipment has not scaled: it remained either low throughput or extremely expensive. With suitable network testing equipment either not at scale or too expensive even for commercial vendors, systems may be released without proper testing and validation. We propose a methodology for large scale testing of networked systems, based on using a low-cost open source network tester and a commodity switch. Our approach is scalable, open source, and accurate, and can be adapted to a variety of networking equipment, widely available to users.