assert doesn't work when raised in class instance

Question

assert doesn't raise an exception when called in an instance of a class:

class TestCaseTest(TestCase):
    ...
    def testFailedResutFormatted(self):
        ...
        assert False    # This doesn't work at all

TestCaseTest("testFailedResutFormatted").run()
assert False    # But this works just fine

Full code can be seen here: http://pastebin.com/Hc9CTTxH

I am obviously doing something wrong, because these are examples from the book and they should work. I just can't figure out what is the matter.

Answer 1

The assert False works just fine, but the AssertionError is caught by the TestCase.run() method, to be collected later.

You didn't pass in a TestResult instance, so in Python 3 the TestCase.run() function returns a new result object for you:

>>> from unittest import TestCase
>>> class TestCaseTest(TestCase):
...     def testFailedResutFormatted(self):
...         assert False
...
>>> tc = TestCaseTest("testFailedResutFormatted")
>>> tc.run()
<unittest.result.TestResult run=1 errors=0 failures=1>

There you see a failure has been recorded.

Pass in a TestResult instance to the TestCase.run() method and it'll be used instead; the result.failures attribute shows the assertion fired and was recorded:

>>> from unittest import TestResult
>>> result = TestResult()
>>> tc.run(result)
>>> result
<unittest.result.TestResult run=1 errors=0 failures=1>
>>> result.failures
[(<__main__.TestCaseTest testMethod=testFailedResutFormatted>, 'Traceback (most recent call last):\n  File "<stdin>", line 3, in testFailedResutFormatted\nAssertionError\n')]
>>> print result.failures[0][1]
Traceback (most recent call last):
  File "<stdin>", line 3, in testFailedResutFormatted
AssertionError