code: def test_ensure_ascii_default(self):
      infile = self._create_infile('{"key":"💩"}')
      outfile = os_helper.TESTFN + ".out"
      self.addCleanup(os.remove, outfile)
      assert_python_ok("-m", "json.tool", infile, outfile)
      with open(outfile, "rb") as f:
          lines = f.read().splitlines()
      # asserting an ascii encoded output file
      expected = [b"{", rb'    "key": "\ud83d\udca9"', b"}"]
      self.assertEqual(lines, expected)
  
imports: import errno
  import os
  import sys
  import textwrap
  import unittest
  import subprocess
  from test import support
  from test.support import os_helper
  from test.support.script_helper import assert_python_ok
label_desc: Use image node_id 15 for calling the TestTool obj's underlying member method code with example usage: obj.test_ensure_ascii_default() without return types