My new article is out!

This time I want to discuss a pretty useful idea for library authors and their users: there are better ways to test your code!

I give three examples (in #python, but the idea itself applies to almost any language) of how user projects can be self-tested without actually writing any real test cases by the end-user. One is hypothetical about django and two examples are real and working: featuring deal and dry-python/returns.

Short example with deal:

import deal

@deal.pre(lambda a, b: a >= 0 and b >= 0)
@deal.raises(ZeroDivisionError)  # this function can raise if `b=0`, it is ok
def div(a: int, b: int) -> float:
    if a > 50:  # Custom, in real life this would be a bug in our logic:
        raise Exception('Oh no! Bug happened!')
    return a / b

This bug can be automatically found by writing a single line of test code: test_div = deal.cases(div). As easy as it gets!

From this article you will learn:
-How to use property-based testing on the next level
- How a simple decorator @deal.pre(lambda a, b: a >= 0 and b >= 0) can help you to generate hundreds of test cases with almost no effort
- What "Monad laws as values" is all about and how dry-python/returns helps its users to build their own monads

I really like this idea! And I would appreciate your feedback on it.
Link: https://sobolevn.me/2021/02/make-tests-a-part-of-your-app