text: import unittest
  
  import responses
  
  from tusclient import client
  
  
  class Mixin(unittest.TestCase):
      @responses.activate
      def setUp(self):
          self.client = client.TusClient('http://master.tus.io/files/')
          url = 'http://master.tus.io/files/15acd89eabdf5738ffc'
          responses.add(responses.HEAD, url,
                        adding_headers={"upload-offset": "0"})
          self.uploader = self.client.uploader('./LICENSE', url=url)
  