Add test_utils file for transition tests

[christophfroehlich]

ros-controls/ros2_controllers#1682

[codecov]

Codecov Report

❌ Patch coverage is 93.10345% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.36%. Comparing base (152ed06) to head (3015cf3).

Files with missing lines	Patch %	Lines
controller_interface/test/test_test_utils.cpp	89.69%	7 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3048      +/-   ##
==========================================
+ Coverage   89.35%   89.36%   +0.01%     
==========================================
  Files         158      160       +2     
  Lines       19392    19538     +146     
  Branches     1573     1576       +3     
==========================================
+ Hits        17327    17460     +133     
- Misses       1419     1428       +9     
- Partials      646      650       +4     

Flag	Coverage Δ
unittests	89.36% <93.10%> (+0.01%)	⬆️

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Files with missing lines	Coverage Δ
...erface/include/controller_interface/test_utils.hpp	100.00% <100.00%> (ø)
controller_interface/test/test_test_utils.cpp	89.69% <89.69%> (ø)

... and 1 file with indirect coverage changes

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[jsantoso91]

Looks good to me, I looked at the design document for the lifecycle found here
https://design.ros2.org/articles/node_lifecycle.html

There are some discrepancies (mentioned in the line comments) for deactivate and cleanup transitions, but since test cases written for these are passing I assume it is just the issue of outdated documentation.

[jsantoso91]

Based on the design document found here https://design.ros2.org/articles/node_lifecycle.html
There is no explicit transition for onDeactivate[FAILURE], but since the test case you wrote for this one seems to PASS I assume the document is the outdated one and the behavior ACTIVE STATE -> Deactivate [Failed] -> ACTIVE STATE is expected.

[christophfroehlich]

there are three return types of the transition callbacks:
https://github.com/ros2/rclcpp/blob/b6e9b4c9b48c48eae09ab79d7b2d4ef95e6c4653/rclcpp_lifecycle/include/rclcpp_lifecycle/node_interfaces/lifecycle_node_interface.hpp#L56-L61

As far as I understood it:

• error: onError transition is called
• failure: no transition is performed (staying in old state).

Here this means that after failure in on_deactivate, it will stay in active mode.

[jsantoso91]

Thank you for sharing the link.
I guess it makes sense when the state transition fails (and no error is thrown), that the state will stay where it is.

[jsantoso91]

Based on the design document found here https://design.ros2.org/articles/node_lifecycle.html
There is no explicit transition for onCleanup[FAILURE], but since the test case you wrote for this one seems to PASS I assume the document is the outdated one and the behavior INACTIVE STATE -> Cleanup [Failed] -> INACTIVE STATE is expected.

[christophfroehlich]

same here, if transition fails it stays in inactive

[jsantoso91]

Is this comment accurate? Based on the diagram included in https://design.ros2.org/articles/node_lifecycle.html
Suppose error is raised during onShutdown() then state will go to ErrorProcessing and further to Unconfigured or Finalized depending on the success/failure of onError.

[christophfroehlich]

this caused some headache, but this was the result of playing around with the tests.

The diagram also shows no [SUCCESS] condition for the shutdown.

[jsantoso91]

I think you meant to say "The diagram also shows no [FAILURE] condition for the shutdown" ?

I think a more accurate comment for the default branch (at least based on the lifecycle diagram) would be
"if transition returns error, the state will end up in the Unconfigured or Finalized depending on the success/failure of onError"

[jsantoso91]

Suggested comment change for L157:

"if transition returns error, the state will end up in the Unconfigured or Finalized depending on the success/failure of onError"

Looks good otherwise.