Hosted run 2243 (dc0a24f2, job 3882) failed in
ModbusWritePduFramingTests.FC16_pdu_is_exactly_header_plus_byte_count with
"Sequence contains no matching element" at transport.Sent.Single(fc == 0x10),
one line after the write had already returned status Good: the driver sent the
FC16 PDU, but the record lost it.
The fixture left Probe at its default (Enabled = true), so InitializeAsync
started ProbeLoopAsync on a pool thread, which sends an FC03 at once. Both that
send and the write's send did List<byte[]>.Add on the capturing transport
concurrently; List is not thread-safe and one Add can overwrite the other.
- Disable the probe in this fixture, as the sibling capturing-transport
fixtures (ModbusProtocolOptionsTests, ModbusCoalescingDefaultsTests) do.
- Record PDUs in a ConcurrentQueue so a background send can never drop one.
- Dispose the driver (await using) so no loop outlives the test.
Test-only; not related to the #729/#727 changes (2243 predates them, and the
run that includes them, 2260, passed Driver.Modbus.Tests 1055/1055).
Claude-Session: https://claude.ai/code/session_01GT67AEHd2Acv1YPwGfXEoV
Joseph Doherty
84e293d2ff