DEP-8

The package ships DEP-8 smoketesting.

In your test VM: 

cd sane-backends-1.0.25/
apt-get build-dep sane-backends
debuild

apt install autopkgtest
# The package insists on having a fully-virtualized environment, can't use "null"
apt install lxc debootstrap rsync ebtables
# Create network
apt install libvirt-daemon-system
# edit /etc/libvirt/qemu/networks/default.xml if needed (IP range...)
virsh net-autostart default
service libvirtd restart
cat > /etc/lxc/default.conf <<'EOF'
lxc.network.type = veth
lxc.network.flags = up
lxc.network.link = virbr0
EOF
# Create base container
autopkgtest-build-lxc debian stretch

# Current package
autopkgtest -B ../sane-backends_1.0.25-4.1.dsc -- lxc autopkgtest-stretch
# New version
autopkgtest -B -- lxc autopkgtest-stretch

Note: currently the test appears to be broken, cf. 968369. 

sed -e /:net/:pnm/ debian/tests/start-net

Internal test-suite

Normally run through dh_auto_test: 

make check

Manual

Plug a physical network or USB scanner to your VM, and try scanning something.

simple-scan or xsane may help.