Regressions tests.

These tests can be run one by one or all togheter.  For separate runs do (for
example):

    python test_modes.py

To run all the tests (ecept test_cleanup.py, which should be run separately) do:

    python testall.py

This last invocation has an optional parameter:

    --random		run the tests in random order

For example:

    python testall.py --random
