feat(hardware_interface): implement dynamic command toggling for MockHardware

[shlok-mehndiratta]

Closes #3214

While working on some controller tests, I realized that the GenericSystem mock always mirrors commands to states perfectly. This makes it hard to test how high-level controllers or state machines react when the hardware actually stops responding or gets stuck (e.g., communication loss or a physical state-lock).

This PR adds a ~/set_command_propagation service (using std_srvs/SetBool) to the GenericSystem mock. It lets you manually "freeze" the command propagation at runtime:

• data: false: The mock stops updating its state and stays at its last value, ignoring new commands.
• data: true: Resumes normal mirroring.

Implementation Notes

• Thread Safety: I used a std::atomic<bool> with memory_order_acquire/release for the toggle. This keeps the real-time read() loop lock-free and safe from the asynchronous service thread without adding mutex overhead.
• Scope: This is strictly for the mock_components/GenericSystem plugin. I haven't tested this on physical hardware since it's a simulation-only feature, and it shouldn't have any side effects on real drivers.
• Testing: I've updated the TestableResourceManager helper to support injecting an executor, which allowed me to verify the service logic in a standard unit test.

I've verified this both with a new test case (toggle_command_propagation_service) and manually with ros2 service call. All 29 existing tests pass.

Hope this helps anyone else trying to simulate hardware gremlins in their tests!

Verification Screenshot

(I'll attach a screenshot here showing the join states freezing after the service call)

[codecov]

Codecov Report

❌ Patch coverage is 76.27119% with 14 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.59%. Comparing base (d93fa51) to head (08806bf).

Files with missing lines	Patch %	Lines
...rface/test/mock_components/test_generic_system.cpp	71.73%	10 Missing and 3 partials ⚠️
...e_interface/src/mock_components/generic_system.cpp	92.30%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3241      +/-   ##
==========================================
+ Coverage   89.56%   89.59%   +0.02%     
==========================================
  Files         168      168              
  Lines       21419    21475      +56     
  Branches     1662     1666       +4     
==========================================
+ Hits        19184    19240      +56     
+ Misses       1533     1530       -3     
- Partials      702      705       +3     

Flag	Coverage Δ
unittests	89.59% <76.27%> (+0.02%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...terface/include/mock_components/generic_system.hpp	100.00% <ø> (ø)
...e_interface/src/mock_components/generic_system.cpp	81.25% <92.30%> (+0.33%)	⬆️
...rface/test/mock_components/test_generic_system.cpp	97.02% <71.73%> (-2.74%)	⬇️

... and 2 files with indirect coverage changes

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[github-actions]

This PR is stale because it has been open for 45 days with no activity. Please tag a maintainer for help on completing this PR, or close it if you think it has become obsolete.

[Copilot]

Pull request overview

This PR enhances the mock_components/GenericSystem mock hardware plugin to allow dynamically enabling/disabling command-to-state mirroring at runtime via a ROS 2 service, enabling more realistic controller/state-machine tests (e.g., simulating “stuck” or unresponsive hardware).

Changes:

• Added a ~/set_command_propagation (std_srvs/SetBool) service to toggle command propagation in GenericSystem.
• Switched the propagation flag to std::atomic<bool> for safe toggling from a service callback.
• Added a new unit test and extended the TestableResourceManager helper to run with an injected executor so the service can be exercised in-test.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
hardware_interface/src/mock_components/generic_system.cpp	Adds the SetBool service and makes the propagation toggle atomic.
hardware_interface/include/mock_components/generic_system.hpp	Declares the atomic flag and service member; adds required includes.
hardware_interface/test/mock_components/test_generic_system.cpp	Adds an executor-driven unit test that toggles propagation via service.
hardware_interface/CMakeLists.txt	Adds std_srvs dependency/targets to build/link configuration.
hardware_interface/package.xml	Declares runtime/build dependency on std_srvs.

Comments suppressed due to low confidence (2)

hardware_interface/test/mock_components/test_generic_system.cpp:2790

• Same issue as above: after joining the executor thread, the test continues past FAIL() and will attempt to join the thread again at the end. Return immediately after FAIL once cleanup is complete.

    {
      executor->cancel();
      executor_thread.join();
      FAIL() << "Service call timed out";
    }

hardware_interface/test/mock_components/test_generic_system.cpp:2774

• Same issue as above: FAIL() does not abort, so the test continues after joining the executor thread and will later join again. Return immediately after FAIL once cleanup is complete.

    {
      executor->cancel();
      executor_thread.join();
      FAIL() << "Service call timed out";
    }

---

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[christophfroehlich]

Thank you, this works as expected!

Please address the comments from copilot if applicable and update the documentation

[christophfroehlich]

This should better be a throttled log.