assertRaises does not catch exception / does not complain about no exception

Question

This code does not work as expected. I'm getting pass when expecting fail; and fail when expecting pass for assertRaises().

test_db.py:

import unittest

class TestConnectDatabase(unittest.TestCase):
    def test_close(self):
        self.assertRaises(ReferenceError, self.close_database()) # <--- Problem #1
        pass

    # Just a stub for brevity...
    def close_database(self):
        #raise Exception(ReferenceError)                         # <--- Problem #2
        pass

if __name__ == '__main__':
    unittest.main()

In this example the code passes the unit test even though the exception was not raised. If #raise is uncommented, the exception is just passed to command line and the test fails when it should pass.

Executing test using: python -m test_db or python test_db.py

@Mark, @DavidCullen: Making sure what's passed in is a reference seems to fix the issue of it not flagging the exception. However, if I uncomment `#raise Exception(ReferenceError)` the test still fails!? ```Traceback (most recent call last): File "C:\...\test_db.py", line 5, in test_close self.assertRaises(ReferenceError, self.close_database) File "C:\Anaconda2\lib\unittest\case.py", line 473, in assertRaises callableObj(*args, **kwargs) File "C:\...\test_db.py", line 9, in close_database raise Exception(ReferenceError) Exception: ``` — kashiraja, Jul 26 '16 at 20:07
Have you tried `raise ReferenceError("This is an error.")` instead of `raise Exception(ReferenceError)`? @kashiraja — Mark, Jul 26 '16 at 23:12
__That does seems to work...awesome!__ I'm really in new territory here.. Thx for your help! — kashiraja, Jul 26 '16 at 23:20
@alecxe This question should probably not be marked duplicate anylonger? — kashiraja, Jul 27 '16 at 17:53

score 1 · Accepted Answer · answered Jul 25 '16 at 23:51

1

You're calling the method self.close_database, when you should just be passing a reference to it. Remove the parentheses e.g.

def test_close(self):
    self.assertRaises(ReferenceError, self.close_database)

Check out the docs for more details.

answered Jul 25 '16 at 23:51

Mark

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score 1 · Answer 2 · answered Jul 25 '16 at 23:52

Remove the parentheses after self.close_database:

class TestConnectDatabase(unittest.TestCase):
    def test_close(self):
        self.assertRaises(ReferenceError, self.close_database)
        pass

You are calling self.close_database which means its result (None) gets passed to assertRaises. See the documentation for assertRaises.

assertRaises does not catch exception / does not complain about no exception

2 Answers2