PyUnit tearDown and setUp vs __init__ and __del__

Question

Is there a difference between using tearDown and setUp versus __init__ and __del__ when using the pyUnit testing framework? If so, what is it exactly and what is the preferred method of use?

Answer 1

setUp is called before every test, and tearDown is called after every test. __init__ is called once when the class is instantiated -- but since a new TestCase instance is created for each individual test method , __init__ is also called once per test.

You generally do not need to define __init__ or __del__ when writing unit tests, though you could use __init__ to define a constant used by many tests.

---

This code shows the order in which the methods are called:

import unittest
import sys

class TestTest(unittest.TestCase):

    def __init__(self, methodName='runTest'):
        # A new TestTest instance is created for each test method
        # Thus, __init__ is called once for each test method
        super(TestTest, self).__init__(methodName)
        print('__init__')

    def setUp(self):
        #
        # setUp is called once before each test
        #
        print('setUp')

    def tearDown(self):
        #
        # tearDown is called once after each test
        #
        print('tearDown')

    def test_A(self):
        print('test_A')

    def test_B(self):
        print('test_B')

    def test_C(self):
        print('test_C')



if __name__ == '__main__':
    sys.argv.insert(1, '--verbose')
    unittest.main(argv=sys.argv)

prints

__init__
__init__
__init__
test_A (__main__.TestTest) ... setUp
test_A
tearDown
ok
test_B (__main__.TestTest) ... setUp
test_B
tearDown
ok
test_C (__main__.TestTest) ... setUp
test_C
tearDown
ok

----------------------------------------------------------------------
Ran 3 tests in 0.000s

OK