How do you test that a Python function throws an exception?

Question

How does one write a unit test that fails only if a function doesn't throw an expected exception?

Answer 1

Use TestCase.assertRaises from the unittest module, for example:

import mymod

class MyTestCase(unittest.TestCase):
    def test1(self):
        self.assertRaises(SomeCoolException, mymod.myfunc)