gistfile1.rb

RSpec::Matchers.define :respond_with_json do |expected|
  match do |actual|
    JSON.parse(actual.response.body) == expected
  end

  failure_message_for_should do |actual|
    "expected the response #{actual.response.body} to be #{expected}"
  end
end

it { should respond_with_json('error' => 'lolcats not found') }