unittest.main() to run all test modules in a package

I have several test modules saved in \tests. I then load them in the main class prior to running the main program by specifying

from tests.ClassTests1 import *
from tests.ClassTests2 import *
...

unittest.main()

Is there any way to instruct unittest.main() to run all the files in \tests without going through endless repetition of importing them as above? E.g. I tried from tests import * and it does not work.

EDIT: I am after the programmatic discovery not the discover via the command-line.

Many thanks!