How to Assert Exception Throwing in Python Functions Using `assertRaises`?

Testing for Exceptions in Python Functions with Assertions

Writing robust code often involves handling exceptions appropriately. Ensuring that functions throw expected exceptions is essential for testing their defensive programming capabilities.

Question: How can I write a unit test that asserts whether a Python function throws a specific exception?

Answer: Utilize the assertRaises method from the unittest module. This method takes two arguments: the expected exception class and the function to be invoked. If the function fails to throw the expected exception under test, the test will fail.

Example:

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

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

In this example, the test method test1 asserts that the function myfunc from the mymod module throws an exception of type SomeCoolException when called. The test fails if the exception is not thrown.

This technique is a concise and effective way to verify the exception-handling capabilities of Python functions, ensuring that they behave as intended in different scenarios.

The above is the detailed content of How to Assert Exception Throwing in Python Functions Using `assertRaises`?. For more information, please follow other related articles on the PHP Chinese website!