DEP-8

The package ships DEP-8 smoketesting, see LTS/TestSuites/autopkgtest for the basic LXC setup.

In your test VM: 

# Test the package you're working on
autopkgtest -B ../sane-backends_1.0.25-4.1+deb9u1_amd64.changes -- lxc autopkgtest-stretch-amd64
# Test the package in the archive (bug in this autopkgtest version / lxc virt-server: should be the same as above)
autopkgtest -B -- lxc autopkgtest-stretch-amd64

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.