docstr: Downloadable files get an additional 'Content-Disposition' header
  that includes their user-specified filename or
  generic filename if filename is not specified.
docstr_tok: ["Downloadable","files","get","an","additional","'Content-Disposition","'","header","that","includes","their","user-specified","filename","or","generic","filename","if","filename","is","not","specified","."]
code: def test_downloadable_file(
      self, file_name, mimetype, content_disposition_header
  ) -> None:
      """Downloadable files get an additional 'Content-Disposition' header
      that includes their user-specified filename or
      generic filename if filename is not specified.
      """
      # Add a downloadable file with an optional filename
      url = self.media_file_manager.add(
          b"mock_data",
          mimetype,
          "mock_coords",
          file_name=file_name,
          is_for_static_download=True,
      )
      rsp = self.fetch(url, method="GET")
  
      self.assertEqual(200, rsp.code)
      self.assertEqual(b"mock_data", rsp.body)
      self.assertEqual(mimetype, rsp.headers["Content-Type"])
      self.assertEqual(
          str(len(b"mock_data")), rsp.headers["Content-Length"]
      )
      self.assertEqual(
          content_disposition_header, rsp.headers["Content-Disposition"]
      )
  
file_path: streamlit/lib/tests/streamlit/web/server/media_file_handler_test.py
imports: from unittest import mock
  from unittest.mock import MagicMock
  import tornado.testing
  import tornado.web
  from parameterized import parameterized
  from typing_extensions import Final
  from streamlit.runtime.media_file_manager import MediaFileManager
  from streamlit.runtime.memory_media_file_storage import MemoryMediaFileStorage
  from streamlit.web.server.media_file_handler import MediaFileHandler
label_desc: Use image node_id 4 for calling the MediaFileHandlerTest obj's underlying member method code with example usage: obj.test_downloadable_file(file_name, mimetype, content_disposition_header) without return types