Find Type Of Exception

Question

I have made a class (derived from Exception):

class InvalidFilterException(Exception):
      #some code here
      super().__init__(message)

Now, when I run tests on this module, using unittest.Testcase , running

assertRaises(Exception, InvalidFilterException, arg1, arg2)

Gives an Error:

AssertionError: Exception not raised by InvalidFilterException

Can someone tell me what should I put in place of Exception as the first argument in assertRaisesso that this test passes? I also tried using InvalidFilterException, as the argument, but that failed too, with the same output.

Your test makes no sense. An exception doesn't raise another exception. You should test that your actual code under test raises InvalidFilterException. — Daniel Roseman, Aug 10 '17 at 08:57
is it because you don't `raise` the exception, only `__init__` it? — Stael, Aug 10 '17 at 08:57
@No changes to the first argument will make that test pass. What do you want to assert actually? — Stop harming Monica, Aug 10 '17 at 09:00
@Stael Whenever i call `InvalidFilterException`, I call it like: `raise InvalidFilterException(arg1,arg2)` — Ayush Shridhar, Aug 10 '17 at 09:11
@Goyo I want to run tests on this module. The first argument should be the type of error that is raised when the function(arg1,arg2) is run, I am not able to pass the test even after passing the type of Exception — Ayush Shridhar, Aug 10 '17 at 09:13
What do you mean? You write a test that calls the code that raises the exception, and wrap it in `assertRaises`. — Daniel Roseman, Aug 10 '17 at 09:17
@AyushShridhar I don't understand what you wat, naybe post a [mcve]. — Stop harming Monica, Aug 10 '17 at 09:18

viveksyngh · Answer 1 · 2017-08-10T09:05:16.383

0

In your case you are trying to InvalidFilterException because the second argument to assertRaises is callable that you want to test.

You need to use your exception like...

assertRaises(InvalidFilterException, do_something, arg1, arg2)

or

with assertRaises(InvalidFilterException):
    do_something(arg1, arg2)

do_something is your function or callable that needs to be tested.

edited Aug 10 '17 at 09:05

answered Aug 10 '17 at 08:59

viveksyngh

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What exactly will the `do_something()` function do? As far as I know, the test will pass if `InvalidFilterException` is raised when `do_something(arg1,arg2)` is run. – Ayush Shridhar Aug 10 '17 at 09:07
Yes .. so the function or block of code that you want to test will be do_something – viveksyngh Aug 10 '17 at 09:30
You can refer to this link for more information... https://stackoverflow.com/questions/129507/how-do-you-test-that-a-python-function-throws-an-exception?rq=1 – viveksyngh Aug 10 '17 at 09:56

Find Type Of Exception

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