The group formed in the London suburb of New Cross in 1981. The core members of the group were Angus Farquhar, Graham Cunnington, Paul Jamrozy, Paul Hines and Toby Burdon. Other members who played with the group at various times included Alistair Adams, Neil Starr, John Eacott, Tony Cudlip, David Coulter, Gus Ferguson and Martin King. Comedian Vic Reeves also played bass in an early incarnation of the band. The slides and film for their multi-media events were the work of their visual director Brett Turnbull.
Their discography spans a wide variety of influences and styles, including a collaboration with the South Wales Striking Miners Choir in support of the miners' strike of 1984. They were particularly notable for complex and powerful percussion, as well as high-energy live performances. Like the German band Einstürzende Neubauten, with whom they are often compared, Test Dept used unconventional instruments such as scrap metal and industrial machinery as sound sources; however, Test Dept's use of these objects was far more rhythmic than was Neubauten's, and was often accompanied by film and slide shows. The group were noted for large-scale events in unusual site-specific locations, such as Waterloo station, Cannon Street station, Stirling Castle and the disused St Rollox Railway Works in Glasgow.