libssh is used by remmina. You can use remmina to establish an ssh
connection to test it.

You can also build the sample applications like so:

install build dependencies:
# apt-get build-dep libssh

create a separate clean source tree:
# cp -a quantal quantal.test
# cd quantal.test
# mkdir build
# cd build
# cmake ..
# make

samplessh: sample ssh client. Type "yes" to accept prompts.
samplesftp: connects to an sftp server and creates a big /tmp/grosfichier file
samplesshd: sample sshd server. Spawn with -p to specify port. Client
 must use user 'aris' with password 'lala'. Use -T on client to disable
 pseudo-tty. Stuff typed into client should print on server side. Must run
 server as root to access host keys. On lucid, must use the libssh sample
 client to test.
libssh_scp: sample scp client
exec: connects locally and does 'lsof'
scp_download: connects locally, creates files in /tmp and fetches them
senddata: connects locally and sends data to /dev/null

Bionic doesn't have a sample ssh server example.

On Cosmic, the samples are different:

./ssh-client username@localhost
./samplesshd-kbdint -d ../../tests/keys/ssh_host_dsa_key -p 1023 127.0.0.1
Authenticate with "libssh" and "libssh". Enter your real name.

On bionic, you can build with testing:

# apt-get build-dep libssh
# apt install libsocket-wrapper libnss-wrapper libuid-wrapper libpam-wrapper
# mkdir build
# cd build
# cmake -DWITH_TESTING=ON -DWITH_CLIENT_TESTING=ON -DWITH_CLIENT_TESTING=OFF ..
# make
# make test

In bionic, a lot of tests fail when -DWITH_CLIENT_TESTING=ON is used.

On Eoan, you can build with testing:

# apt-get build-dep libssh
# apt install libsocket-wrapper libnss-wrapper libuid-wrapper libpam-wrapper
# mkdir build
# cd build
# cmake -DUNIT_TESTING=ON -DCLIENT_TESTING=ON -DSERVER_TESTING=ON ..
# make
# make test

In Eoan, torture_proxycommand fails.

You can run a single test with debugging:

# /usr/bin/ctest --force-new-ctest-process -VV --debug -R torture_scp