Comment 90 for bug 1736116

Steps performed (only on amd64 hw, no i386 testing performed).

1) Install a clean Ubuntu 16.04.4 LTS amd64 iso.
2) Reboot
3) upgrade and dist-upgrade
4) enable proposed
5) install only virtualbox virtualbox-ext-pack virtualbox-guest-utils-hwe virtualbox-guest-x11-hwe
6) enable 3d on guest properties
6) reboot, and check if everything still works as expected
7) run virtualbox inside the guest and try to install a VM inside the VM, this verifies the host functionalities
8) remove guest-utils and install the official guest-additions package
9) reboot
A) check again if everything works as expected
B) kbuild doesn't need to be tested, because it was upgraded just to make the new one build correctly

For artful, testing was similar, except that I tested virtualbox-guest-utils virtualbox-guest-x11 instead of the -hwe packages.

Missing testing:
different hw (we did test on two laptops, one with windows host, one with linux host)
i386
xenial non-hwe (kernel 4.4 and virtualbox-guest* non -hwe packages). They were fine the first time I checked them, nothing should have changed and nobody reported issues so far

I'm not sure they are worth the effort, since we got already a lot of positive feedbacks and zero negative ones