def METHOD_NAME(self, testdata):
    """
    Tests whether or not enforcing the byte order while reading and writing
    does something and works at all. Using the wrong byte order will most
    likely raise an Exception.
    """
    # This file is little endian.
    file = testdata['1.su_first_trace']
    # The following should both work.
    su = _read_su(file)
    assert su.endian == '<'
    su = _read_su(file, endian='<')
    assert su.endian == '<'
    # The following not because it will unpack the header and try to unpack
    # the number of data samples specified there which will of course not
    # correct.
    with pytest.raises(SEGYTraceReadingError):
        _read_su(file, endian='>')