A C-based test suite can be found in the tests subdirectory. It uses the automake testing harness to execute the tests.
A default set of tests that are always expected to pass can be executed by doing
make check
An extended test suite that includes some tests that may fail occasionally can be enabled at configure time:
./configure --enable-extended-test-suite make check
A few test cases require additional packages to be installed. In particular, several IO tests assume /usr/bin/vi is available as an input file and will fail if it is not present.