A quick look at the Relay Buddy kit #191 from Electronic Specialties (ES). This kit simplifies the process of testing relays, though it requires 12 volts dc for power. I suspect a simple AC to 12v DC adapter would work for this as a custom modification. The adapters I mentioned in the video as having side terminals for checking voltage and amp draw are from Lisle (link below) and come in several variants.

(affiliate links)
Relay Buddy (alone) https://amzn.to/2SMO8Cp
Relay Buddy (kit) https://amzn.to/2LL40ow
Lisle relay adapters with side terminals:
Kit I: https://amzn.to/2JWXHMl
Kit II: https://amzn.to/2SP36I7
Both: https://amzn.to/2LMdCiF