Assertion class for testing JSON content.

have_json.rb

class HaveJson
  def initialize(selector)
    @selector = selector
  end

  def matches?(json)
    @json = json
    return traverse(@json, @selector)
  end

  def description
    "find selector in JSON"
  end

  def failure_message
    "Expected JSON to include: #{@selector}.\nClosest node found: #{@last_node}.\n" + actual
  end

  def actual
    @actual.present? ? "Test: #{@test} Actual: #{@actual}\n" : ""
  end

  def negative_failure_message
    "Found: #{@selector} in JSON string. Expected nil."
  end

private
  def traverse(json, path)
    path.split('/').inject(json) do |value, selector|
      if selector.include? '='
        selector, test = selector.split('=')
        set_value(value, selector)
        unless value.to_s == test
          @test = test
          @actual = value.to_s
          return nil
        end
      else
        set_value(value, selector)
      end
    end
  end

  def set_value(value, selector)
    value = value[selector] rescue nil
    @last_node = selector
  end
end

def have_json(selector)
  HaveJson.new(selector)
end