ModbusSimulatorFixture default port bumped from 502 to 5020 to match the pymodbus convention. Override via MODBUS_SIM_ENDPOINT for a real PLC on its native 502. Skip-message updated to point at the new Pymodbus\serve.ps1 wrapper instead of 'start ModbusPal'. csproj <None Update> rule swapped from ModbusPal/** to Pymodbus/** so the new JSON profiles + serve.ps1 + README copy to test-output as PreserveNewest.
standard.json — generic Modbus TCP server, slave id 1, port 5020, shared blocks=false (independent coils + HR address spaces, more textbook-PLC-like). HR[0..31] seeded with address-as-value via per-register uint16 entries, HR[100] auto-increments via the built-in increment action with parameters minval=0/maxval=65535 (drives subscribe-and-receive integration tests so they have a register that ticks without a write — pymodbus's increment ticks per-access not wall-clock, which is good enough for a 250ms-poll test), HR[200..209] scratch range left at 0 for write tests, coils 0..31 alternating, coils 100..109 scratch. write list covers 0..1023 so any test address is mutable.
dl205.json — AutomationDirect DirectLOGIC DL205/DL260 quirk simulator, slave id 1, port 5020, shared blocks=true (matches DL series memory model where coils/DI/HR overlay the same word address space). Each quirky register seeded with the pre-computed raw uint16 value documented in docs/v2/dl205.md, with an inline _quirk JSON-comment naming the behavior so future-me reading the file knows why HR[1040]=25928 means 'H' lo / 'e' hi (the user's headline string-byte-order finding). Encoded quirks: V0 marker at HR[0]=0xCAFE; V2000 at HR[1024]=0x2000; V40400 at HR[8448]=0x4040; 'Hello' string at HR[1040..1042] first-char-low-byte; Float32 1.5f at HR[1056..1057] in CDAB word order (low word first); BCD register at HR[1072]=0x1234; FC03-128-cap block at HR[1280..1407]; Y0/C0 coil markers at 2048/3072; scratch C-relays at 4000..4007.
serve.ps1 wrapper — pwsh script with a -Profile {standard|dl205} parameter switch. Validates pymodbus.simulator is on PATH (clearer message than the raw CommandNotFoundException), validates the profile JSON exists, builds the right --modbus_server/--modbus_device/--json_file/--http_port arg list, and execs pymodbus.simulator in the foreground. -HttpPort 0 disables the web UI. Foreground exec lets the operator Ctrl+C to stop without an extra control script.
README.md fully rewritten for pymodbus: install command (pip install 'pymodbus[simulator]==3.13.0' — pinned for reproducibility, [simulator] extra pulls aiohttp), per-profile reference tables, the same DL205 quirk → register table from PR 42 but adjusted for pymodbus paths, what's-NEW-vs-ModbusPal section (all four tables, raw uint16 seeding, declarative actions, custom Python action modules, headless, web UI, maintained), trade-offs section (float32-as-two-uint16s for explicit CDAB control, increment ticks per-access not wall-clock, shared-blocks mode for DL205 vs separate for Standard), file-format quick reference for hand-authoring more profiles. References pinned to the pymodbus readthedocs simulator/config + REST API pages.
docs/v2/modbus-test-plan.md harness section rewritten with the swap rationale; PR-history list updated to mark PR 42 SUPERSEDED by PR 43 and call out PR 44+ as the per-quirk implementation track. Test-conventions bullet about 'don't depend on ModbusPal state between tests' generalized to 'don't depend on simulator state' and a note added that pymodbus's REST API can reset state between facts if a test ever needs it.
DL205Profile.cs and DL205SmokeTests.cs xml-doc updated to reference pymodbus / dl205.json instead of ModbusPal / DL205.xmpp.
Functional validation deferred — Python isn't installed on this dev box (winget search returned no matches for Python.Python.3 exact). JSON parses structurally (PowerShell ConvertFrom-Json clean on both files), build clean, .json + serve.ps1 + README all copy to test-output as expected. User installs pymodbus when they want to actually run the simulator end-to-end; if pymodbus rejects the config the README's reference link to pymodbus's simulator/config schema doc is the right next stop.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
ModbusSimulatorFixture is a collection fixture so the 2s TCP probe runs once per run, not per test; SkipReason gets a clear operator-facing message ('start ModbusPal or override MODBUS_SIM_ENDPOINT'). Tests call Assert.Skip(sim.SkipReason) rather than silently returning — matches the test-plan convention and reads cleanly in CI logs. DL205Profile.BuildOptions deliberately disables the background probe loop since integration tests drive reads explicitly and the probe would race with assertions. Tag naming uses the DL205_ prefix so filter 'DisplayName~DL205' surfaces device-specific failures at a glance.
Project references: xunit.v3 + Shouldly + Microsoft.NET.Test.Sdk + xunit.runner.visualstudio (matches the existing Driver.Modbus.Tests unit project), project ref to src/Driver.Modbus. Registered in ZB.MOM.WW.OtOpcUa.slnx under tests/. ModbusPal/README.md documents the dev loop (install ModbusPal jar, load profile, start simulator, dotnet test), explains MODBUS_SIM_ENDPOINT override for real-PLC benchwork, and flags DL205.xmpp as the first profile to add in a follow-up PR.
dotnet test run against the scaffold (no simulator running) skips cleanly: 0 failed, 0 passed, 1 skipped, with the SkipReason surfaced. dotnet build clean (0 warnings, 0 errors). Updated docs/v2/modbus-test-plan.md to mark the scaffold PR done and renumbered future PRs from 'PR 27+' to 'PR 31+' to stay in sync with the actual PR chain.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
