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import struct
import pytest
from umodbus.client.serial.redundancy_check import (get_crc, validate_crc,
CRCError)
def test_get_crc():
""" Test if correct CRC is calculated. """
# Values are equal to those used in example in MODBUS over serial line
# specification and implementation guide V1.02, chapter 6.2.2.
assert struct.unpack('<H', get_crc(b'\x02\x07')) ==\
struct.unpack('<H', b'\x41\x12')
def test_validate_valid_crc():
"""" Method should not raise assertion error. """
validate_crc(b'\x00\x01\x02\xf1\x91')
def test_validate_invalid_crc():
"""" Method should raise assertion error. """
with pytest.raises(CRCError):
validate_crc(b'\x01\x02\x07')
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