Pre-requisites

a Debian Bookworm (or newer) system
a user that has sudo credentials
Install perl5lib's dependencies

Install dependencies needed to generate IUKs, UDFs, and to run the test suite

cat $(git rev-parse --show-toplevel)/config/chroot_local-packageslists/tails-iuk.list \
   | grep -E -v '^#' \
   | xargs sudo apt --yes install && \
sudo apt install \
   libdist-zilla-plugin-test-notabs-perl \
   libdist-zilla-plugin-test-perl-critic-perl \
   libdist-zilla-app-command-authordebs-perl \
   libtest-lwp-useragent-perl && \
sudo apt update && \
cd "$(git rev-parse --show-toplevel)/config/chroot_local-includes/usr/src/iuk" && \
dzil authordebs --install && \
sudo apt install \
   libarchive-tools \
   libdevice-cdio-perl \
   dosfstools \
   faketime \
   gdisk \
   genisoimage \
   gnutls-bin \
   kpartx \
   libdata-dumper-concise-perl \
   libdatetime-perl \
   libfile-copy-recursive-perl \
   nginx \
   python3-xattr \
   squashfs-tools-ng=1.2.0-1 \
   syslinux

Run the test suite

Prepare your environment (which includes getting a sudo authentication token, that's needed by the test suite, and setting a umask that runs the tests in conditions closer to production):

export SOURCE_DATE_EPOCH=$(date --utc +%s)
cd "$(git rev-parse --show-toplevel)/config/chroot_local-includes/usr/src/iuk" && \
export TORSOCKS_CONF_FILE=$PWD/torsocks.conf
sudo true
umask 077

Run the full test suite:

cd "$(git rev-parse --show-toplevel)/config/chroot_local-includes/usr/src/iuk" && \
TAILS_GIT_CHECKOUT="$(git rev-parse --show-toplevel)" \
PERL5LIB="${TAILS_GIT_CHECKOUT}/config/chroot_local-includes/usr/src/perl5lib/lib" \
   LC_ALL=C.UTF-8 \
   dzil test --all

To run only BDD tests (ala Cucumber) defined under config/chroot_local-includes/usr/src/iuk/features, use pherkin. For example:

cd "$(git rev-parse --show-toplevel)/config/chroot_local-includes/usr/src/iuk" && \
TAILS_GIT_CHECKOUT="$(git rev-parse --show-toplevel)" \
PERL5LIB="${TAILS_GIT_CHECKOUT}/config/chroot_local-includes/usr/src/perl5lib/lib" \
   LC_ALL=C.UTF-8 \
   pherkin features/download_upgrade-description_file

Test manually

To test automatic upgrades on an image that includes changes to our Upgrader, typically you need to make the running Tails under test system believe it's running an older version of Tails, that can be upgraded.

To do so:

Install the Tails image you want to test on a USB drive.
Start Tails from that USB drive.
Set an Administration Password.
Create a copy of the file that the Upgrader uses to tell which version of Tails was initially installed on this USB stick:
```
 install -m 644 /lib/live/mount/rootfs/filesystem.squashfs/etc/os-release /tmp/
```
Modify /tmp/os-release

Typically, you would set VERSION to the version of the last-but-one Tails release.

Mask the 2 real os-release files with your own:

 sudo cp /tmp/os-release /etc/os-release && \
 sudo mount -o bind /tmp/os-release /lib/live/mount/rootfs/filesystem.squashfs/etc/os-release

Restart the Upgrader service:

 systemctl --user restart tails-upgrade-frontend.service