A fixture that passes bad units is worse than no fixture at all, because it converts a quality problem into a documented false confidence.
End-of-line test is the last honest moment in a build. Everything before it is process; everything after it is packaging. So the fixture that performs that test carries more weight than its cost suggests, and it deserves the same scrutiny as the product.
Validation starts with known-good and known-bad units. A fixture that passes good units proves very little on its own — the interesting question is whether it fails the failures. We seed deliberate defects: a missing connection, an out-of-range component, a swapped polarity, and confirm that the test catches each one and reports it as the correct fault rather than as a generic failure.
Then comes repeatability. The same unit tested ten times should give the same verdict, and the measured values should sit comfortably inside the limits rather than hovering at the edge. A test that passes at 0.98 of its limit will start failing good units the day the ambient temperature changes.
Finally, the fixture needs an owner and a life. Contacts wear, cables fatigue, reference units drift. We record fixture verification alongside calibration, so that a test result from three years ago can be traced to a fixture that was known to be working — which is the whole point of testing in the first place.
— GANI Contract Manufacturing engineering team