new_contents: from flask import Flask
  from flask_webapi import WebAPI, APIView, renderer, route
  from flask_webapi.renderers import PickleRenderer
  from unittest import TestCase
  
  
  class TestRenderer(TestCase):
      def setUp(self):
          self.app = Flask(__name__)
          self.api = WebAPI(self.app)
          self.api.load_module('tests.test_renderers')
          self.client = self.app.test_client()
  
      def test_pickle_renderer(self):
          response = self.client.post('/add')
          self.assertEqual(response.status_code, 200)
          self.assertEqual(response.headers['content-type'], 'application/pickle')
  
  
  class BasicView(APIView):
      @route('/add', methods=['POST'])
      @renderer(PickleRenderer)
      def add(self):
          return {}
  
subject: Add unit tests for pickle renderer