Abstract: An on-board tester (referred to as a “test fixture”) for testing integrated circuit chips, particularly ball grid array (BGA) chips. The test fixture of the present invention eliminates many of the problems associated with presently available test fixtures, particularly the lack of control in mounting the chips to the test fixture, and the unpredictable testing results. The present test fixture has an upper assembly and a lower assembly. A circuit board containing the BGA chip to be tested is mounted between the upper and lower assemblies. The lower assembly has guide pins extending toward the upper assembly which allows any circuit board having alignment holes that match the configuration of the guide pins to be mounted to the lower assembly. Moreover, the present test fixture has a unique latching mechanism which uses rotational movement to latch and unlatch the test fixture.