[Article] Monkey Patching is not too bad - pytest plugin example

article-monkey_patching_is_not_too_bad-has_trace_example.py

from returns.result import Result, Success, Failure

def example_function(arg: str) -> Result[int, str]:
    if arg.isnumeric():
        return Success(int(arg))
    return Failure('"{0}" is not a number'.format(arg))

def test_if_failure_is_created_at_example_function(returns):
    with returns.has_trace(Failure, example_function):
        Success('not a number').bind(example_function)