Q: What is this directory? A: It contains so-called "system-level" tests for pytddmon. Q: What do you mean, "system level"? A: It means that they excercise pytddmon "as a whole", rather than testing it's parts, as the ordinary unit-tests do (those that are called test_*.py in pytddmon root directory) Q: Why a 'systest' directory? Why not put them among the other test_*.py files? A: To clearly separate unit-level tests from system-level tests. Q: How are the system level tests run? A: The tests in this directory are not meant to be run by pytddmon. Run them with the systest.py script: $ python systest.py It will output which tests worked and which failed. Q: How is this organized? A: The systest.py script runs pytddmon.pyw in "test mode" (flag --log-and-exit) inside all subdirectories of systest. In each directory, there is an "expected.log" file. That file contains the correct output for pytddmon, for the directory in question. systest.py checks each and every expected.log, and compares it with the newly created pytddmon.log. For each broken expectation, an informative message is printed to stdout. Besides any test and/or code-files in the folder being tested, an optional "args.txt" may specify any arguments to pytddmon.