For most things a basic, DC continuity test is the first "go/no go" test. If a cable doesn't pass that, it won't pass any subsequent bandwidth test...
"Real" testing for non-CAT cables is expensive. I watched a recent YT vid of testing HDMI cables to see if they met the various standards over a variety of lengths. A revealing test, but the box that tests those... a "budget" machine at that... sells for about US$16,000 with some accessories. Add some i/o panels and you can test Thunderbolt® and assorted USB cables, DisplayPort cables, few others.
But the $16k price tag puts it out of reach for a lot of AV and production folks who could use what it does.
