There are a variety of tests, some more automated than others.
Running make check gets you all of them. Warning: some of them
take a very long time to run. Generally speaking most of the tests
should be interpreted to fail if xconq dumps core, and succeed in most
other cases (some error messages might be considered failures).
Perhaps the most interesting tests are the autotests. These are written in a unit test style, meaning that the test code links into the code under test, which is good for speed and makes it easy to test particular parts of the code rather than end-to-end behaviors. They should run fast enough to run them every time you make a change to xconq.
To run just the autotests:
$ cd kernel $ make skelconq $ cd ../test $ make check-auto