Are there ways to test if the cable that I have is a working Thunderbolt 3 cable?
Yes. Purchase a cable from a known vendor with a reputation for quality. I tend to stick with Anker, Cables2Go (C2G), Belkin, and Pluggable (cables, not peripherals) and even Apple (well, whoever Apple selected to OEM for them).
C|Net summarized it perfectly in their article Here's everything you need to know about USB-C and Thunderbolt 3:
- All Thunderbolt 3 cables will work as USB-C cables.
- All USB-C cables will work as Thunderbolt 3 cables as long as they are good quality cables.
It’s when you start rummaging around in the bargain bin looking for low cost USB and Thunderbolt cables that you end up with cables that just don’t work the way they’re supposed to. Spend the few extra dollars up front and it’s something you won’t have to worry about (meaning spending hours diagnosing and days waiting for your delivery from <insert favorite online retailer here>)
If you plug a TB cable into a TB3 port and hook it up to a USB device, it’s going to show in the “USB section.” Likewise, plug it into the same port but now the device is a TB device (like a dock), ot will show up in the “Thunderbolt section.” In other words, the cable doesn’t define how the device appears -the device snd the port do. It’s also important to remember that Thunderbolt 3 carries USB 3.1 but not the other way around.
As for your LG cable, I wouldn’t preclude it being of suspect quality. Just physically comparing the Apple cable (which I already owned) and the LG cabled included in the box, the Apple cable was clearly of higher quality. I’ve chucked more “included” cables because of horrible build quality than I care to remember. Remember, a lot of this is to meet a requirement, check off a box on a list somewhere and most folks won’t notice the difference