Add missing tests for pendulum and gripper (position and effort) (backport #814)

[Vanjoseluis]

This PR adds several missing integration tests for the demos in gz_ros2_control_demos.

Included tests

• Pendulum position test
• Gripper position test
• Gripper effort test

These tests follow the same structure as the existing demo tests:

• verify that /joint_states is published
• verify that controllers are loaded and active
• check initial joint state when applicable
• launch the example node and ensure it exits cleanly

---

Additional fixes

• updated launch files to correctly accept gz_args
• updated CMakeLists.txt to install and register the new tests
• applied the same fix to pendulum_position_test that was required for pendulum_effort_test in backport Add initial_value checks to state interface tests (backport #765) #781

Backport
This is a backport of pull request #814.

[christophfroehlich]

tests are failing

[Vanjoseluis]

Humble CI is failing because it is trying to run tests whose corresponding demo launch files do not exist in the Humble branch.

In particular,

gripper_mimic_joint_example_effort.launch.py
gripper_mimic_joint_example_position.launch.py

are referenced by the test suite but were never added to Humble’s gz_ros2_control_demos.

The other tests are passing in CI.
Let me know if you prefer to skip these tests on Humble or handle this in a separate PR.

[christophfroehlich]

Can you add the missing files here please? Maybe just a backport was forgotten, than you can cherry-pick the respective commit into your branch.

[Vanjoseluis]

Humble never received PR #276, so the later commits that updated these demos did not apply to Humble. I cherry‑picked PR #276 and accepted only the incoming changes related to the new launch files.
The new launch files were then updated to match the current Jazzy versions so that the test suite can find and load them correctly.

---

I’m reviewing and reverting some mistakenly added changes in gz_system.cpp and index.rst.
Only the missing demo launch, YAML, and URDF files should be part of this backport, so I’ll restore Humble’s original implementation and keep the scope limited to the demo files.

[christophfroehlich]

Tests are failing, I guess that 276 introduced some (intended) behavior change.

[Vanjoseluis]

Humble never received PR #276, so the later commits that updated these demos did not apply to Humble. I cherry‑picked PR #276 and accepted only the incoming changes related to the new launch files. The new launch files were then updated to match the current Jazzy versions so that the test suite can find and load them correctly.

I’m reviewing and reverting some mistakenly added changes in gz_system.cpp and index.rst. Only the missing demo launch, YAML, and URDF files should be part of this backport, so I’ll restore Humble’s original implementation and keep the scope limited to the demo files.

Summary of updates in the last commit:

• Restored gz_system.cpp and index.rst to their original versions from upstream/humble.
• Updated the gripper demo YAML and URDF files to match the versions in upstream/jazzy (the original backport had incomplete URDF content).

CI results
All tests passed in:

• build (fortress)
• build (fortress, -testing)
• build (harmonic, -testing, gz_ros2_control.humble.repos)

The apt-get install failures are inconsistent across jobs (packages install successfully in the passing jobs).

[christophfroehlich]

CI results All tests passed in:

* build (fortress)

This is not true ;)

2026-05-04T14:57:25.3894851Z 4: ./launch/gripper_mimic_joint_example_position.launch.py:119:7: W292 no newline at end of file
2026-05-04T14:57:25.3896287Z 4: 
2026-05-04T14:57:25.3897222Z 4: ./launch/gripper_mimic_joint_example_effort.launch.py:119:7: W292 no newline at end of file

and pre-commit is failing with the same error.

The apt-get install failures are inconsistent across jobs (packages install successfully in the passing jobs).

Yes, the build farm is on fire due to the lyrical release. Hopefully this settles soon.

[christophfroehlich]

tests are green now, but pre-commit is still failing.

[christophfroehlich]

Thank you!