old_contents: import os.path
  
  from tornado.testing import gen_test
  
  from thumbor_plugins.test_helpers.engine import EngineCase
  
  
  class GIFVTest(EngineCase):
      optimizer = "thumbor_plugins.optimizers.gifv"
      fixtures_path = os.path.join(os.path.dirname(__file__), "imgs")
  
      @gen_test
      async def test_gifv(self):
          await self.http_client.fetch(
              self.get_url("/unsafe/filters:gifv()/animated.gif")
          )
  
new_contents: import os.path
  
  from tornado.testing import gen_test
  
  from thumbor_plugins.test_helpers.engine import EngineCase
  
  
  class GIFVTest(EngineCase):
      optimizer = "thumbor_plugins.optimizers.gifv"
      fixtures_path = os.path.join(os.path.dirname(__file__), "imgs")
  
      @gen_test
      async def test_gifv(self):
          response = await self.http_client.fetch(
              self.get_url("/unsafe/filters:gifv()/animated.gif")
          )
          self.assertEqual(response.code, 200)
          self.assertEqual(response.headers["Content-Type"], "video/mp4")
  
      @gen_test
      async def test_gifv_with_background(self):
          response = await self.http_client.fetch(
              self.get_url("/unsafe/filters:gifv(mp4):background_color(ff00ff)/animated.gif")
          )
          self.assertEqual(response.code, 200)
          self.assertEqual(response.headers["Content-Type"], "video/mp4")
  
      @gen_test
      async def test_gifv_webm(self):
          response = await self.http_client.fetch(
              self.get_url("/unsafe/filters:gifv(webm)/animated.gif")
          )
          self.assertEqual(response.code, 200)
          self.assertEqual(response.headers["Content-Type"], "video/webm")
  
subject: Add WebM tests