[RQT_JTC] add unit tests for parse_joint_limits

[lakhmanisahil]

Closes #2253

What this PR does

get_joint_limits() read from a global description variable set only by a ROS topic subscription — impossible to unit test without a live node.

This PR extracts all parsing logic into a new pure function parse_joint_limits(urdf_string, ...) that takes the URDF directly as a string with no ROS dependency. get_joint_limits() becomes a thin wrapper that reads the global and delegates to it. The minidom parsing logic itself is unchanged.

Files changed

File	Change
joint_limits_urdf.py	Extract parse_joint_limits() from get_joint_limits()
test/test_joint_limits_urdf.py	23 pytest tests, fully ROS-free
test/__init__.py	New (marks test dir as Python package)
package.xml	Add python3-pytest test dependency

Tests (23 total, all passing)

• Revolute joint — correct min/max position, velocity, limit flag
• Continuous joint — defaults to ±π when no bounds given
• Fixed joints — silently ignored
• Multiple mixed joints — all handled correctly
• safety_controller soft limits — narrowed when flag is True, ignored when False
• Mimic joints — excluded from free_joints
• Missing <limit> for a required joint → raises with clear message
• Missing lower/upper on revolute → raises (minidom returns "", our code raises)
• Missing velocity → raises (same reason — our logic, not minidom's)

[codecov]

Codecov Report

❌ Patch coverage is 91.89189% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.19%. Comparing base (6c1299f) to head (68fda72).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
...t_joint_trajectory_controller/joint_limits_urdf.py	78.18%	8 Missing and 4 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2281      +/-   ##
==========================================
+ Coverage   84.72%   85.19%   +0.46%     
==========================================
  Files         153      154       +1     
  Lines       15362    15457      +95     
  Branches     1332     1334       +2     
==========================================
+ Hits        13016    13169     +153     
+ Misses       1858     1797      -61     
- Partials      488      491       +3     

Flag	Coverage Δ
unittests	85.19% <91.89%> (+0.46%)	⬆️

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

Files with missing lines	Coverage Δ
...ajectory_controller/test/test_joint_limits_urdf.py	100.00% <100.00%> (ø)
...t_joint_trajectory_controller/joint_limits_urdf.py	77.33% <78.18%> (+77.33%)	⬆️

... and 1 file with indirect coverage changes

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[christophfroehlich]

This looks very good, I only have some questions..

[lakhmanisahil]

Hello @christophfroehlich, I’ve responded to the suggested changes. PTAL and let me know if anything else is needed.
I’ll update the PR accordingly.

[lakhmanisahil]

Hey @christophfroehlich, i have addressed the suggested changes, PTAL.
Thank You

[christophfroehlich]

Thank you, now it looks perfect!