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.

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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