How to Test for Expected Exceptions in Python Functions?

Testing Exceptions in Python Functions

Problem:

How to ensure that a Python function raises an expected exception?

Answer:

Use the TestCase.assertRaises method from the unittest module. This method takes two arguments: the exception class and the function call. If the function call does not raise the expected exception, the test fails.

Here's an example:

<code class="python">import unittest
import mymod

class MyTestCase(unittest.TestCase):
    def test1(self):
        self.assertRaises(SomeCoolException, mymod.myfunc)</code>

In this example, test1 asserts that the function myfunc in module mymod raises an exception of type SomeCoolException. If the exception is not raised, the test will fail.

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