How to check if my El Capitan back-up is valid?

[JorisHoogsteder]

So before trying to update to (High) Sierra from El Capitan, I CCC'd my startup disk (named "MainDrive") to an external drive (plus I have a Timemachine running internally on a separate drive).

Though, I wanted to check if the backup was bootable - I did install/update Clover to the harddrive, but once I select the actual ext. drive in my bios, it goes into the bootloader (the Clover screen), but yet I still only see "boot MacOS from MainDrive"!

Am I forgetting about something? I just want to check if everything works fine before I start making the leap to Sierra

 

[BreBo]

@JorisHoogsteder, please update your profile (personal details) with your Motherboard or Make/Model, CPU and Graphics Card.

Profiles need to contain at least your primary system to assist others with helping you.