Advice for people wanting to wire electric water pump. Tap into the pink wire that powers the air pump. This is what you would do if you were to use/follow Gary's EWP harness. I used a the painless harness BTW.
Sure, now a days they are cheap. Continuity is not actually resistance. It just indicates the circuit is 'continuous' eg not broken. And test lights are still fine for 12v ckts and gnds, if you understand what you're doing.
Unless resistance is other than zero ,or infinite. Then it's a problem ,and a test light will indicate circuit is good.... Which is why (almost) nobody uses a test light ,or voltmeter to verify integrity of circuitry.