loose_json_comparison.rb

module JsonSpec::Matchers

  def look_like(json = nil)
    JsonSpec::Matchers::LookLike.new(json)
  end

  class LookLike < BeJsonEql

    def matches?(actual_json)
      raise "Expected equivalent JSON not provided" if @expected_json.nil?

      @actual, @expected = scrub(actual_json, @path), scrub(@expected_json)
      flexible(parse_json(@expected)) == parse_json(@actual)
    end

    def flexible(hash)
      hash.each do |key, value|
        if value.is_a?(String) && value == '*'
          hash[key] = NotNil.new
        elsif value.is_a?(Hash)
          hash[key] = flexible(value)
        end
      end
      hash
    end

  end

  class NotNil

    def initialize
      @compared = "<not compared>"
    end

    def ==(other)
      @compared = other.nil? ? "*" : other
      !other.nil?
    end

    def to_s
      @compared.inspect
    end

  end
end

This allows specifying attributes that you want to ensure are there, but that you don't really care about the value of.

eg.

expect(response_body).to look_like <<-JSON
  {
    "access_token": "*",
    "token_type": "bearer",
  }
JSON