Show HN: PBT – A property-based testing library for Ruby (opens in new tab)

Yeah, the easiest way is to generate attributes and instantiate any Rails model like the one below:

    Pbt.assert do
      Pbt.property(name: Pbt.printable_string, age: Pbt.integer(min: 0, max: 100)) do |name:, age:|
        user = User.new(name: name, age: age)
        # write your test here
      end
    end

Outside of language level preferences, is there something about the ecosystem around Ruby that makes it particularly well suited to this? I would have thought Python was the glue language winner just because there are already bindings to the entire universe available for it.

So, this means refactoring becomes potentially difficult. While the gem is still a great accomplishment and very useful, I'd have to engineer my way around this issue before using it with things like a Rails Model which could have changing shape.

@OP:

I wonder if the README (and possibly runner) should suggest writing a test-case that doesn't rely on PBT when the user wants to preserve a case for future testing.

The issue here is that if you're saving a singular example and it represents a weird corner case, it's totally conceivable that a small change will result in an invisible change to that test case.

Another idea: it'd be great if the test could simply take examples that are failing and add them to a `failing_examples.rb` or some such. I know I'd use a feature like this quite a bit.

>yes, because you're changing the order in which the random draws are interpreted. But this isn't a problem in practice because you generally aren't changing the generator in the middle of debugging a failure.

Correct. The test inputs are determined by a seed and generators (including the order of generators).