Test if a function throws an exception in Python

Test if a function throws an exception in Python

In Python, you can test if a function throws an exception using the pytest framework, which is a popular testing tool in the Python ecosystem.

Here's a step-by-step guide on how to test if a function throws an exception:

  • Install pytest:

    First, you need to install pytest if you haven't already:

pip install pytest

  • Write the function:

    Let's say we have the following function named divide:

def divide(a, b): return a / b

  • Write the test:

    Now, let's write a test to check if the divide function throws a ZeroDivisionError when we try to divide by zero:

import pytest from your_module import divide # Import the function from your module def test_divide_throws_exception(): with pytest.raises(ZeroDivisionError): divide(1, 0)

Here, the with pytest.raises(ZeroDivisionError): block checks if the code inside it raises the specified exception.

  • Run the test:

    Navigate to the directory containing your test file and run the test using the pytest command:

pytest your_test_filename.py

If the divide function throws a ZeroDivisionError when dividing by zero, the test will pass. If it doesn't, the test will fail.

You can follow this pattern to test other exceptions and other functions in a similar way.

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