Pytest Testing Idioms

Internal

• Pytest

Tested Code is Supposed to Throw Exception

import pytest

def test_something_that_should_throw_exception():
    with pytest.raises(Exception) as info:
        my_method()

If the tested code raises a more specific exception, you can use that instead:

def test_something_that_should_throw_exception():
    with pytest.raises(ValueError) as info:
        my_method()

This tests the exception arguments:

def test_something_that_should_throw_exception():
    with pytest.raises(ValueError) as info:
        my_method()
    # important: interaction with 'info' must take place outside the with block
    assert info.value.args[0] == "some message"
    assert "some message" in str(info.value)

Also see:

Python Language | Exceptions