Workflow to test the quality of XLR microphone cables, and have a quantitative measure of this quality
No. Pad the line level signal down by 40 to 60dB, and amplify it after the cable in a decent professional mic amp (which you have previously tested) set to the same gain as your pad, not the &quot;mic in&quot; on your soundcard.

The pad should present low (maybe 20 or 100 ohm) and 600 ohm impedance to the cable.
In addition to your prescribed test:

Repeat with 48V DC common mode to represent phantom power.

Check for microphonics. Especially with phantom power applied, and no signal, jump on the cable, flex it around, and hit it with a hammer. You shouldn't hear any thumps or noises : the cable itself isn't meant to act as a microphone.

Run a long cable from a thyristor dimmer at half power to a 5 kW studio spotlight, twisted several times around the cable under test. Note the level of buzz picked up in the cable. Probably only &quot;star quad&quot; cable (allegedly developed at the BBC where it's known as &quot;blue quad&quot;) will be satisfactory on this test. That may or may not matter depending on your recording location.