CODEWITHSUNDEEP
pythonpython-unittest
Joy
Joy

Reputation: 4511

Using assertRaises without self in Python 3.6

I would like to test one failure scenario in one of my python file as follows:

source.py

def myfunc():
     a()

associated test.py

def testMyFuncException():
     a = Mock()
     a.side_effect = MyError
     with self.assertRaises(MyError) as _ : <--- THIS LINE I CANNOT USE self.assertRaises
       ..

But here I cannot use self as it's not associated with any class. So I am not getting any clue regarding how to do this.

EDIT

I have done it as follows now as per suggestions:

def testMyFuncException(TestCase):
     a = Mock()
     a.side_effect = MyError
     with TestCase.assertRaises(MyError) as _ :
     ...

Now I am getting error as follows:

E       fixture 'TestCase' not found

Upvotes: 6

Views: 2952

Answers (3)

Robin Winslow
Robin Winslow

Reputation: 11522

You don't need pytest. Although TestCase.assertRaises does need to be run against a TestCase instance, it doesn't use or need any context that varies from instance to instance. You can use any old TestCase object.

Meaning you can just do this:

from unittest import TestCase

with TestCase().assertRaises(MyError):
    raise_myerror()

Or, in the context of your example above:

from unittest import TestCase

def testMyFuncException():
    a = Mock()
    a.side_effect = MyError
    with TestCase().assertRaises(MyError):
        raise MyError

Upvotes: 0

MrBean Bremen
MrBean Bremen

Reputation: 16885

Another possibility is to use pytest instead of unittest. In this case you don't need a separate test class:

import pytest
from unittest.mock import Mock

def test_myfunc_exception():
    a = Mock()
    a.side_effect = MyError
    with pytest.raises(MyError, match="my exception message"):
        ...

Upvotes: 8

dspencer
dspencer

Reputation: 4481

You need a TestCase fixture in the unittest testing framework. The normal way to do this is to create a class inheriting from unittest.TestCase. You will then be able to use the self.assertRaises method, along with the other asserts in the TestCase class:

from unittest import TestCase
from unittest.mock import Mock

class TestMyFunc(TestCase):
    def test_myfunc_exception(self):
        a = Mock()
        a.side_effect = MyError
        with self.assertRaises(MyError) as _ :
        ...

Upvotes: 0

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