How to Test if a Python Function Throws a Specific Exception?

Testing Python Functions for Exception Throwing

Unit testing in Python often involves verifying the behavior of functions under various conditions, including the raising of expected exceptions. To test if a function throws a specific exception, one can utilize the assertRaises method provided by the unittest module. This method allows developers to assert that an exception will be raised, failing the test if the exception is not thrown.

The syntax for assertRaises is as follows:

<code class="python">assertRaises(exception_class, function, *args, **kwargs)</code>

Where:

• exception_class: The expected exception class to be thrown.
• function: The function under test.
• args and kwargs: Arguments and keyword arguments to be passed to the function.

For example, to test whether a function myfunc raises a SomeCoolException when called, one can write a unit test as follows:

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

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

In this test, assertRaises is used to assert that myfunc will raise a SomeCoolException when called without any arguments. If myfunc does not raise the expected exception, the test will fail.

The above is the detailed content of How to Test if a Python Function Throws a Specific Exception?. For more information, please follow other related articles on the PHP Chinese website!