idk if the app has been redesigned since 2018, the designs/behavior look similar, but it started as a vue app with d3 and topojson to render the reporting units, visual diffs and some basic unit testing i dunno if vitest was around in 2018 but whatever the equivalent is, but elections are not like any other software, and changes are made at the last minute no matter how disciplined you might be- the real thing was to test, test, test by hand on a spare screen before going to air, often times on set with a few seconds to spare