Get a USBC voltmeter dongle from amazon. Best $20 I've spend:

https://www.amazon.com/gp/product/B01NAWYSVK

UPDATE: actually, no, the displays is upside down on one of my devices! Duh! A cheap gyroscope would help, or another OLED screen on the back but in the opposite direction (as USBC-cables are reversible)

If you spend a bit more, you can find ones that will trigger USB-PD without you having to plug a device in. Will also test the various protocols like Qualcolm's Quick Charge, Huawei's FCP, Samsung's AFC, etc.

Can I ask which one you recommend? (hopefully readable when you only have USB-C ports on the right handside)

This one is going back to Amazon.

That will tell you the basics, but you will still miss things like transients. Still it gives useful information.

> the displays is upside down on one of my devices!

wait I don't get it. It's USB-C, just flip it over?

The ports are only on the right hand side. The voltmeter screen always display in the same orientation. So if I flip it over, it will display correctly instead of upside down, but only the person sitting in front of me will be able to read it as the display will be facing the back of the screen of the laptop

It is a simple USB-C design oversight from Pluggable that a simple gyroscope or extra screen would have fixed easily.

Try plugging it in to the left side of your computer instead of the right side.

Try buying me a new laptop?

what if you turned both the dongle and your laptop upside down?