How to use the cmd2.utils.StdSim function in cmd2

def CreateOutsimApp():
    c = cmd2.Cmd()
    c.stdout = utils.StdSim(c.stdout)
    return c

def test_history_transcript():
    app = CmdLineApp()
    app.stdout = StdSim(app.stdout)
    run_cmd(app, 'orate this is\na /multiline/\ncommand;\n')
    run_cmd(app, 'speak /tmp/file.txt is not a regex')

    expected = r"""(Cmd) orate this is
> a /multiline/
> command;
this is a \/multiline\/ command
(Cmd) speak /tmp/file.txt is not a regex
\/tmp\/file.txt is not a regex
"""

    # make a tmp file
    fd, history_fname = tempfile.mkstemp(prefix='', suffix='.txt')
    os.close(fd)

    # tell the history command to create a transcript

def exit_code_repl():
    app = ReplWithExitCode()
    app.stdout = utils.StdSim(app.stdout)
    return app

def sc_app():
    c = SubcommandsExample()
    c.stdout = utils.StdSim(c.stdout)
    return c

def ac_app():
    app = AutoCompleteTester()
    app.stdout = StdSim(app.stdout)
    return app

def test_stdsim_line_buffering(base_app):
    # This exercises the case of writing binary data that contains new lines/carriage returns to a StdSim
    # when line buffering is on. The output should immediately be flushed to the underlying stream.
    import os
    import tempfile
    file = tempfile.NamedTemporaryFile(mode='wt')
    file.line_buffering = True

    stdsim = cu.StdSim(file, echo=True)
    saved_size = os.path.getsize(file.name)

    bytes_to_write = b'hello\n'
    stdsim.buffer.write(bytes_to_write)
    assert os.path.getsize(file.name) == saved_size + len(bytes_to_write)
    saved_size = os.path.getsize(file.name)

    bytes_to_write = b'hello\r'
    stdsim.buffer.write(bytes_to_write)
    assert os.path.getsize(file.name) == saved_size + len(bytes_to_write)

ex: app('help')
        :param command: command line being run
        :param echo: if True, output will be echoed to stdout/stderr while the command runs
                     this temporarily overrides the value of self.cmd_echo
        """
        if echo is None:
            echo = self.cmd_echo

        # This will be used to capture _cmd2_app.stdout and sys.stdout
        copy_cmd_stdout = StdSim(self._cmd2_app.stdout, echo)

        # Pause the storing of stdout until onecmd_plus_hooks enables it
        copy_cmd_stdout.pause_storage = True

        # This will be used to capture sys.stderr
        copy_stderr = StdSim(sys.stderr, echo)

        self._cmd2_app.last_result = None

        stop = False
        try:
            self._cmd2_app.stdout = copy_cmd_stdout
            with redirect_stdout(copy_cmd_stdout):
                with redirect_stderr(copy_stderr):
                    stop = self._cmd2_app.onecmd_plus_hooks(command, pyscript_bridge_call=True)
        finally:
            with self._cmd2_app.sigint_protection:
                self._cmd2_app.stdout = copy_cmd_stdout.inner_stream
                self.stop = stop or self.stop

        # Save the output. If stderr is empty, set it to None.
        result = CommandResult(stdout=copy_cmd_stdout.getvalue(),