def isolated(func):
def wrapped(func, runner, *args, **kwargs):<EOL><INDENT>with runner.isolated_filesystem():<EOL><INDENT>with open('<STR_LIT>', '<STR_LIT:w>') as f:<EOL><INDENT>f.write('<STR_LIT>')<EOL><DEDENT>return func(runner, *args, **kwargs)<EOL><DEDENT><DEDENT>return decorator.decorator(wrapped, func)<EOL>
Runs a method in an isolated filesystem.

    This also stubs out an app.json for convenience.