An apparatus for testing a wafer or chip comprising a photonic integrated circuit comprises: an electrical signal interface module comprising an array of movable conducting structures; a photonic signal interface module attached to the electrical signal interface module, the photonic signal interface module comprising one or more optical fiber interfaces, and a first set of grating couplers arranged over at least a first plane of the photonic signal interface module; and one or more electrical signal connections between the electrical signal interface module and the photonic signal interface module.