Phased array feeds enable radio telescopes to make faster surveys with fewer antennas. This paper presents testing of a phased array feed prototype to verify design methods for array feeds of the Australian Square Kilometre Array Pathfinder (ASKAP). We have tested a 5 × 4 port × 2 polarisation connected-chequerboard array at the prime focus of a 12 m diameter parabolic reflector. This prototype system currently achieves a system-temperature-on-efficiency ratio Tsys/η of 134 K at 1260 MHz and operates from 700 MHz to 1,800 MHz. The larger 94 port × 2 polarisation phased array feed being developed for ASKAP has a target Tsys/η of 50 K. The time taken by a radio telescope to survey a fixed area of sky to a fixed sensitivity is proportional to (Tsys/η)2.