How to test drive macOS Catalina in an APFS partition?

As an iOS developer I really want to try the live view for SwiftUI in Xcode 11 in macOS Catalina.

Unfortunately Parallels Desktop does not support this combi (yet), as Xcode 11 crashes on start.

This procedure mentioned by Marco Arment might work:

I’m not sure how to do this. New partition? New volume?

Did anyone try this and can (s)he share the steps involved?

You should be able to use Edit | Add APFS Volume in Disk Utility to add a volume to the container.

Another thought is installing on an external USB drive Apple.

There are articles around about using Box and VMWare to run Catalina on Windows 10, so you might try one of those if Parallels doesn’t support it yet.

I’ve always done this using an external drive. I clone my Mac’s drive to the external, boot to the external, then download and install the beta OS on the external. When you first boot to the external, check the startup applications and remove them – you won’t want mail, for instance, going to the test partition! Also disable Time Machine and any other backup app.

By “always” I’ve done this with OS betas from Snow Leopard to Catalina.

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I’m using an external Samsung T5 1Tb SSD via USB-C for Catalina.

WAY faster than a flash drive and honestly can’t tell the difference running Catalina on the external SSD vs Mojave on the internal SSD

I formatted an external SSD with APFS, then told the Catalina installer to use the SSD. Zero delays and it isn’t the fastest SSD out there.

I just finished installing Catalina on an external SSD (Samsung T5). After the installation the first 2 tries to restart resulted in the circle with line through it icon at startup, but it worked on the third go.

This might help (me) as well:

And this might be the answer to my original question:

(did not try this yet)

And Apple has instructions as well; they even mention installing a beta OS:

A couple of things to report so far.
My Catalina is installed on an external SSD. When this is connected via an OWC Dock, it wont boot - instead it gives the prohibited disk symbol (circle with line through). When connected directly to the MBP, it boots as expected.
Secondly, when an iPad is connected to the computer via the Finder there’s no way I could find to see the iPad’s serial number or device ID as required to register the iPad for the iPadOS beta, in either the Finder or Music app. However you can copy it from About This Mac / System Report / USB.

You don’t need to register the device for the beta, do you? Just download the image, connect the device to iTunes (Finder on Catalina?), Option-Click update or restore and select the image.

All you need is Xcode 11 Beta installed.