Abstract: A fixture for testing of an MMIC-containing package includes an alignment plate, a pogo-pin assembly, a waffleline support baseplate, and a pressure engagement assembly. The alignment plate contains a pattern of apertures that matches that of the pins of the MMIC-containing package and defines, with those pins, transmission lines having an impedance that effectively matches that of the internal interconnect to the MMICs within the package. The alignment plate is mounted atop a pogo-pin assembly, pogo-pins of which are aligned with signal conductors of the package, and which form transmission lines having an impedance effectively matching the impedance of the transmission lines through the alignment plate. The pogo-pin assembly engages a waffleline structure in a baseplate. The baseplate includes coaxial connectors that are coupled to channels of the waffleline and joined to the pogo-pins.