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import pytest
from serial import Serial
from time import time
from pymeasure.adapters import SerialAdapter
class TestSerialLoopback:
"""Test serial adapter with two real but looped COM ports.
A pair of COM ports that are looped will read the written data from the other.
This looping needs to be done outside this script. One suggestion is using the application
`com0com <https://com0com.sourceforge.net/>`_.
Alternatively two UART adapters could be used, that have their RX/TX physically connected.
Call PyTest with the argument``--device-address="COM1,COM2"`` to specify the serial addresses,
minding the comma for the separation of the two ports.
"""
ADAPTER_TIMEOUT = 1.0 # Seconds
@pytest.fixture()
def adapter(self, connected_device_address):
device = connected_device_address.split(",")[0]
return SerialAdapter(
device,
baudrate=19200,
timeout=self.ADAPTER_TIMEOUT,
read_termination=chr(0x0F),
)
@pytest.fixture()
def loopback(self, connected_device_address):
"""See `adapter()`."""
device = connected_device_address.split(",")[1]
return Serial(device, baudrate=19200)
def test_read(self, adapter, loopback):
"""Regular read with fixed number of bytes."""
loopback.write(b"abc")
result = adapter.read_bytes(3)
assert len(result) == 3
@pytest.mark.parametrize("data", [
b"a", # Short data
b"aaaaabbbbbccccceeeee" * 50, # A lot data
b"a" * 256, # Exactly one chunk size
b"aaaaabbbbb\nccccceeeee" * 50, # With a newline (should be ignored)
])
def test_read_all(self, adapter, loopback, data):
"""Read with undefined number of bytes - also confirm timeout duration is correct."""
loopback.write(data)
start = time()
result = adapter.read_bytes(-1)
elapsed = time() - start
assert result == data
assert self.ADAPTER_TIMEOUT == pytest.approx(elapsed, abs=0.1)
@pytest.mark.parametrize("chunk", [1, 256, 10000])
def test_read_varied_chunk_size(self, adapter, loopback, chunk):
"""Read with undefined number of bytes with non-default chunk size."""
data = b"abcde" * 10
loopback.write(data)
result = adapter.read_bytes(-1)
assert result == data
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