Question

Can someone explain this result to me. The first test succeeds but the second fails, although the variable tested is changed in the first test.

>>> class MyTest(unittest.TestCase):     def setUp(self):         self.i = 1     def testA(self):         self.i = 3         self.assertEqual(self.i, 3)     def testB(self):         self.assertEqual(self.i, 3)   >>> unittest.main() .F ====================================================================== FAIL: testB (__main__.MyTest) ---------------------------------------------------------------------- Traceback (most recent call last):   File '<pyshell#61>', line 8, in testB AssertionError: 1 != 3  ---------------------------------------------------------------------- Ran 2 tests in 0.016s 

Answer 1

Each test is run using a new instance of the MyTest class. That means if you change self in one test, changes will not carry over to other tests, since self will refer to a different instance.

Additionally, as others have pointed out, setUp is called before each test.