Rspec custom argument matcher

json_including_argument_matcher.rb

class Hash
  def deep_include?(sub_hash)
    sub_hash.keys.all? do |key|
      self.has_key?(key) && if sub_hash[key].is_a?(Hash)
        self[key].is_a?(Hash) && self[key].deep_include?(sub_hash[key])
      else
        self[key] == sub_hash[key]
      end
    end
  end
end

module JsonIncluding
  class JsonIncluding
    def initialize(json)
      @json = json
    end

    def ==(other_json)
      JSON.parse(other_json).deep_include?(JSON.parse(@json))
    end

    def inspect
      "#{@json.to_s}"
    end
  end

  def json_including(json)
    JsonIncluding.new(json)
  end
end

RSpec.configure do |config|
    config.include JsonIncluding
end

describe 'blah' do
  it "updates the applicant in connection-orders" do
    json = ({applicant: {first_name: nil}}).to_json
    expect(client).to receive(:update).with(json_including(json), 1234)
    order.save
  end
end