Abstract: A probe and test socket assembly wherein spring biased plunger probes of extraordinarily small diameter, such as 0.02 inch, are densely packed into a test socket for testing of integrated circuit chips. The socket is constructed in upper and lower halves with bores to receive the probes. To manufacture probes of such small diameter and to provide minimal and constant electrical resistance, the plungers and barrel of the probes are not crimped or otherwise secured together. The configuration of the socket bore walls in combination with the probe maintains the probe plunger and barrel together. The assembly is particularly useful in densely packed arrays of extremely fine diameter probes for testing densely packed test sites.