Abstract: An earthquake early warning system, ShakeAlert, is providing alerts to beta end users in the western United States. Earthquake early warning algorithms have to undergo rigorous real-time and off-line testing before being accepted into the ShakeAlert production system. Real-time in situ tests ensure functionality in the current seismic environment and the robustness of candidate code. The off-line tests use a data suite of historical events, based on point-source assessments and ground-motion predictions assessments to give a comprise stress test of candidate code to assess if the code is production ready.