"Testify!" is a song recorded, co-written, and produced by British DJ Hifi Sean, featuring American singer and co-writer Crystal Waters, which was recorded in both London and Washington, D.C.. Taken from HiFi Sean's 2016 debut album "Ft.", the Gospel-themed single reached number one on Billboard's Dance Club Songs chart in its October 7, 2017 issue, giving Waters her eleventh chart topper, as well as the first number one for HiFi Sean.