PBT

In this session, we're going to discover Property-Based Testing.

Instructions

Let's redo some kata we've already tried and see how PBT can change the way we approach the problem.

We're going to use Eris as our PBT tool. It will generate multiple random values to try falsifying our properties. In case of a property being falsified it will shrink the values to try to get a simpler example.

Try writing tests for some properties we've discussed using Eris

Here are some ideas but feel free to try your own ones :

• Repeating a string twice give a string twice as long as the original one
• Reversing a string twice gives the same string
• A sorted list is the same length of the original list
• Monday + 7 days is a Monday

Try seeing the generated values (with a debugger or var_dump) and create a bug just to see the shrinking in action. You can play with the view_shriking test.

Password validation

https://www.codurance.com/katalyst/password-validation

FizzBuzz

https://github.com/ardalis/kata-catalog/blob/main/katas/FizzBuzz.md

Got more time ?

Imagine some examples with what you know with the business rules your work on every day.

Resources

If you want to learn more about Property-Based Testing you can find resources here.

Getting started

Run composer install to get dependencies.

Alternatively, you can install dependencies using docker with docker-compose run --rm php composer install.

Run tests

You can run tests with PhpUnit using ./vendor/bin/phpunit.

If you prefer using docker you can run tests with docker-compose run --rm php ./vendor/bin/phpunit.