Feature Request: Add API for testing Array size

[PikachuEXE]

I am using json_spec currently and just started using this gem.

I like how I can validate the types easily with expect_json_types.
But I found no API for Array size, which is very common when writing spec for collection endpoints.
(Like expect_json_size)

I am staying with have_json_size from json_spec at the moment.

[brooklynDev]

Hey @PikachuEXE, I appreciate your feedback, but I'm afraid of feature creep. This is already possible with airborne using a block like so:

it 'should validate array size' do
  get '/array_api' #api that returns {data: [1,2,3,4]}
  expect_json_types({data: -> (data){expect(data.length).to eq(4)}}
end

I'll admit it's not as nice as having a specialized function for array size, but I don't think we should add a function for every variation that people come across. This was the intent of the blocks, where you can just use RSpec's robust expectation library.

I'm open to feedback though, and if you/others disagree, I'll reconsider.

[PikachuEXE]

I have added one to a wiki page.

[brooklynDev]

OK, I've changed my mind 😄 I took a look at your code, and I like it, I was thinking about going with a different approach that would have been slightly more invasive.

Go ahead and submit a pull request (please add tests and documentation as well) and I'll merge it. Thanks for the effort!

[PikachuEXE]

I tried adding internal methods but didn't work for unknown reason.
But since you already have a way/example for custom validation, I thought let's don't waste it.

PR will be created later.

[brooklynDev]

Thanks for your pull request. I'm closing this issue since I've merged your pull request: #18