The right way to do this is a cable tester. Modest ones cost like $1000. Still outside hobbyist budget.
The not so right way to do this is to get a $50 connection tester like the Ideal one at Home Depot, this device will tell you if the right wires on one end connect to the right place on the other, that is, if its wired and crimped correctly. That right there eliminates many common problems. Beyond that, try to use the link with two reasonably good 1000BaseT (gigabit) NICs and pump data through it, looking for any errors counted by the hardware such as FCS errors or short frames.