rack_app_spec.rb

test_app = lambda do |env|
  [200, 
    {'Content-Type' => 'text/html',
    'Content-Length' => '3'}, ['Yes']]
end

describe test_app, 'RackApp' do

  it { should respond_to(:call) }
  
  context '#call' do

    let(:response) { subject.call({}) }
    let(:http_status) { response[0].to_i }
    let(:http_header) { response[1] }
    let(:http_body) { response[2] }

    it do
      response.should be_an(Array)
      response.should have_exactly(3).items
    end

    context 'response HTTP status' do

      it do
         http_status.should be_an(Integer)
         http_status.should > 100
      end

    end

    context 'response HTTP headers' do

      it do
        http_header.should respond_to(:each)
        http_header_string = ''

        http_header.each do |key, value|
    
          http_header_string << key    
            
          key.should be_a(String)
          key.should_not eq('Status')
          key.should_not =~ /:\n/
          key.should_not =~ /[-_]$/
          key.should =~ /^[a-zA-Z]{1}[\w]+/

          value.should be_a(String)
          value.should =~ /[\n]*/
          value.should_not =~ /[\000-\037]/
        end
        
        no_content_statuses = [204, 304, *(100...200)]

        http_header_string.should include 'Content-Type' unless no_content_statuses.include? http_status
        http_header_string.should include 'Content-Length' unless no_content_statuses.include? http_status

      end

    end


    context 'response HTTP body' do

      it "won't break in ruby 1.9" do
        http_body.should_not be_a(String)
      end

      it do

        http_body.should respond_to(:each)

        http_body.each do |element|
          element.should be_a(String)
          element.to_path.should be_a(String) if element.respond_to? :path
        end

      end

    end

  end

end