We have two different options for creating Virtual Machines, Virtual Box and Vagrant. You can choose one of the two options below.

Virtual Box

Install Virtual box and run Debian Sid in it.

sudo apt install virtualBox

For Manual installation, download Debian Testing ISO from Debian website and install it inside already installed VirtualBox. Once you have Debian Testing, you can upgrade it to Sid/unstable.

Edit /etc/apt/sources.list and change testing to sid or unstable.

apt update
apt dist-upgrade

Vagrant

If you want to make your job easy just install vagrant

sudo apt install vagrant-libvirt libvirt-daemon-system

Make sure that you are having only single Hypervisor running otherwise be ready to see some error. Also, vagrant installation might ask you to install some other additional packages, allow it to do so.

Add your user to libvirt group to use vagrant without additional privillege prompts

sudo gpasswd -a <your user> libvirt

Create a new directory from where you want to start VM. vagrant will store some configuration file in that directory and then switch to that directory

mkdir /path/to/directory/packaging
cd /path/to/directory/packaging

Now we need to tell vagrant where we need to fetch Vagrant box (VM image)

You can find recent Debian Testing vagrant box on the following URL https://app.vagrantup.com/debian/boxes/testing64

vagrant init debian/testing64
vagrant up

Note: This can take some time depending on your internet connection speed.

Then you can connect to the VM by

vagrant ssh

Note: Current image is very old, so you will need to run apt update and apt dist-upgrade (to update debian-archive-keying) before you can upgrade to sid.

You can update to Sid by replacing testing with sid in /etc/apt/sources.list and running

apt update
apt dist-upgrade

Note: If you use nfs to share host directory with the vm, then you'll need rpc-statd service or you may get no locks available error message.

sudo systemctl enable rpc-statd  # Enable statd on boot
sudo systemctl start rpc-statd  # Start statd for the current session