Running a Python unittest test on multiple files

I want to add unit testing to the assessment of my high school programming class.

If I have twenty submissions of files that look like this:

def calculateReturn(principle, rate, freq, time):
    final = principle * (1 + (rate/freq)) ** (freq * time)
    return final

Can I use a test case like this?

import unittest

class test(unittest.TestCase):
    def test1(self):
        value = calculateReturn(5000, 0.05, 12, 11)
        self.assertAlmostEqual(value, 8235.05, 2)

if __name__ == '__main__':
    unittest.main()

How do I run this one simple test on twenty modules?

FURTHER INFORMATION

For testing I have created three "submissions" all of which show different ways of calculating x^y.

submission1.py:

from math import pow

def powerFunction(base, power):
   result = pow(base, power)
   return result

submission2.py:

def powerFunction(base, power):
    result = base ** power
    return result

submission3.py:

def powerFunction(base, power):
    result = 1
    for i in range(power):
        result = result * base

    return result

The test code is:

import unittest
import importlib

class MyTest(unittest.TestCase):
    def setUp(self):
        pass

    def test_power_3_4(self):
        self.assertEqual(module.powerFunction(2, 3), 8)

files = ['submission1', 'submission2', 'submission3']
for file in files:
    module = importlib.import_module(file)
    print module
    unittest.main()

if the test code is run the console output shows only submission1 being tested:

/System/Library/Frameworks/Python.framework/Versions/2.7/bin/python2.7
/Users/staff/PycharmProjects/UnitTest/powerTest.py
<module 'submission1' from '/Users/staff/PycharmProjects/UnitTest/
submission1.pyc'>
.
----------------------------------------------------------------------
Ran 1 test in 0.000s

OK

Process finished with exit code 0

Interestingly if I don't use unit testing I can correctly import and test using this approach:

import importlib

files = ['submission1', 'submission2', 'submission3']

for file in files:
    module = importlib.import_module(file)
    print module
    print module.powerFunction(2,3)

The console output here is:

/System/Library/Frameworks/Python.framework/Versions/2.7/bin/
python2.7 /Users/staff/PycharmProjects/UnitTest/importlib1.py
<module 'submission1' from '/Users/staff/PycharmProjects/UnitTest/
submission1.pyc'>
8.0
<module 'submission2' from    '/Users/staff/PycharmProjects/UnitTest/
submission2.pyc'>
8
<module 'submission3' from   '/Users/staff/PycharmProjects/UnitTest/
submission3.pyc'>
8

Process finished with exit code 0

It may well be that the unittest module is not the best approach here but I'm still interested on how to implement it.