PLCSIM.UnitTest

PLC unit testing, from engineering to automation.
One test workflow. A desktop workbench and CLI. Extensible access profiles.

Repeatable unit tests for PLC code, from interactive debugging to automated builds. PLCSIM.UnitTest executes the tests defined in a PLC project and turns their events into structured results.

• Regression testing: repeat tests after PLC code changes and identify failed assertions.
• Failure analysis: retained lifecycle and communication evidence for investigating incomplete or failed runs.

Desktop Workbench — WPF

• Session configuration, repeated test runs, result inspection and runtime diagnostics.
• Application-managed engineering or testing against a PLC program prepared externally.

Automation — CLI

• PLC tests as a pipeline step: configured project preparation, transfer and test execution without an interactive UI.
• A job result CI can act on: exit codes distinguish successful runs, failed tests and infrastructure errors.
• Reports retained on failure: JUnit output remains available for artifact collection and downstream test-report processing.

GitHub Actions job excerpt for a provisioned Windows runner with exclusive access to its test runtime and the project/configuration already available:

runs-on: [self-hosted, Windows, plcsim]
steps:
  - name: Run PLC tests
    shell: pwsh
    run: |
      $results = 'artifacts/plcsim-unittest/${{ github.run_id }}-${{ github.run_attempt }}'
      & 'C:\Program Files\PLCSIM.UnitTest\PLCSIM.UnitTest.App.Cli.exe' run --file .\ci\unittest.json --output "$results/junit.xml"
      exit $LASTEXITCODE
  - name: Retain JUnit report
    if: always()
    uses: actions/upload-artifact@v4
    with:
      name: plc-test-results
      path: artifacts/plcsim-unittest/${{ github.run_id }}-${{ github.run_attempt }}/junit.xml
      if-no-files-found: ignore

Each job attempt has its own result path. A failed test fails the execution step; the upload step still retains the report when one was produced. Uploading stores the XML artifact; test-report visualization is configured separately in CI.

Complete CI starters include provisioning guidance, preflight and runtime serialization for

• GitLab CI
• GitHub Actions
• Jenkins
• Azure Pipelines
• TeamCity

Test Results — JUnit XML

Both applications export reconstructed PLC test results as JUnit XML. Suites, cases, assertion failures and errors can be consumed by CI test-report views.

Illustrative export with example test names and timings:

<testsuites name="PLC UnitTests" tests="2" failures="1" errors="0" skipped="0" time="0.035">
  <testsuite name="MotorControl" tests="2" failures="1" errors="0" skipped="0" time="0.035">
    <testcase classname="MotorControl" name="StartMotor" time="0.025" />
    <testcase classname="MotorControl" name="StopMotor" time="0.010">
      <failure message="Motor output remained active">Expected FALSE, observed TRUE.</failure>
    </testcase>
  </testsuite>
</testsuites>

Failure Analysis

• Run Analysis links failed assertions and incomplete evidence to affected suites and test cases, separating observed facts, conclusions and suggested checks.
• Exportable evidence: a snapshot ZIP contains analysis.md, events.ndjson and, for run analysis, hierarchy.json for further investigation.

Illustrative, shortened Run Analysis for the StopMotor failure above:

Run Evidence Analysis
Assessment: Error

[Error] UnitTest failures observed
Observed facts:
  [first-failing-assertion] StopMotor/MotorOutputOff: Expected FALSE, observed TRUE.
Deterministic conclusions:
  [test-result-not-passed] At least one UnitTest owner or finding did not pass.
Suggested checks:
  Inspect assertion 'MotorOutputOff' in test case 'StopMotor'
  and verify its reported actual and expected inputs.

Evidence analysis also covers PLC lifecycle and communication-health reports. Suggested checks are grounded in retained evidence; they do not assert an unobserved PLC-internal cause.

Current PLC Targets

PLC target	Runtime environment	Integration and PLC framework
Siemens SIMATIC S7-1500	Local PLCSIM Advanced simulation.	Siemens profile + S7UnitTest
Beckhoff TwinCAT 3 PLC	TwinCAT 3.1 Build 4026, existing local Usermode Runtime.	Beckhoff profile + Tc3UnitTest

The PC application and the matching PLC framework are both required. Tests, assertions and orchestration execute on the PLC.

Note

The linked framework repositories are currently private and empty while publication is being prepared.

Exact engineering/runtime versions, supported operations and qualification limits belong to the linked profiles and their bindings.

Concept And Integration

• A shared core: both applications use the same workflow and result model, keeping test interpretation consistent across interactive and automated runs.
• Access profiles as plugins: a selected directory package supplies project access, runtime control and UnitTest lifecycle/event communication through common service contracts.
• Vendor isolation: engineering and runtime API dependencies stay inside the integration, keeping WPF, CLI and shared result processing independent of vendor types.
• Independent composition: Siemens combines TIA Openness and PLCSIM Advanced bindings; Beckhoff integrates TwinCAT engineering and ADS communication in one package. Compatible new profiles extend the available environments.
• A testable foundation: the Fake profile exercises the shared workflow without vendor installations.

flowchart LR
    UI[WPF / CLI] --> Core[Shared workflow and results]
    Core <--> Profile[Selected access profile]
    Profile <--> Runtime[Vendor engineering and PLC runtime]
    Core --> Output[JUnit XML and diagnostics]

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Project Status

Windows distribution 2.0.1: a FIFO event-buffer fix updates the PLCSIM Advanced V6/V7/V8 bindings and workers to 2.0.1. The WPF and CLI application remains 2.0.0; the other component versions are unchanged. See the 2.0.1 release notes and verification scope.

Download the Windows installer. The 2.0.0 release notes remain available for the previous distribution.

Further Reading

• Technical project specification: system requirements, technology stack and repository structure.
• Documentation guide: installation, WPF/CLI operation, profiles, development and packaging.
• Architecture: shared models and integration boundaries.

Support this project

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License

Created by Lorenz Software and available under the MIT license. Distributed third-party components retain their own licenses; see release license sources.