New starter or new to you (used)?
How well is the starter body grounded? The front should be considered isolated because of the O-ring. The rear of the starter body, and the mounting bracket it all bolts to should be clean, bare metal (no paint, metallic coatings OK). At least the starter case and bracket anyway.The bolts going into the case will do the rest, paint on the side cover where the bracket bolts is fine.
If wanting to test the condition of a cable, you can voltage drop test it with a simple voltmeter. Live positive or negative cable, it doesn't matter as long as it's loaded to operational conditions.
Both voltmeter leads go on the same wire. For instance, testing the ground cable, put one lead on the cable at the battery and the other lead on the cable where it bolts to the frame or engine. Engage the starter and record the voltage on the meter, you'll see the difference, how much voltage you're loosing from one end to the other. It works the same on positive cables.
There are easy to find voltage drop charts online, based on cable material (copper, aluminum, tinned copper, copper coated aluminum, etc.), gauge, and length.
No need to remove a cable or mess with anything else, just hook up the voltmeter, record, and research. Resistance tests on larger cables is unreliable, this is the much better method, faster, and requires less work.
The story of three wheels and a man...