add unit tests for sub-command tab completer

[fujitatomoya]

This is not issue, but minor enhancement for tab complete Classes to integrate with unit tests.

in ros2cli, there are several tab completers for sub-commands such as ActionTypeCompleter, ComponentTypeNameCompleter and so on. Unfortunately these tab completion classes are not tested for now, that brought the #1169 for an instance.

We can add unit tests for each tab completer to make sure if the class works okay just like #1172 that includes ParameterNameCompleter.

related to #1172, especially #1172 (comment)

[fujitatomoya]

CC: @christophebedard

[ros-discourse]

This issue has been mentioned on Open Robotics Discourse. There might be relevant details there:

https://discourse.openrobotics.org/t/ros-news-for-the-week-of-january-19th-2026/52057/1

[jan10010]

Hi! I’m new to contributing to ROS 2, and I’d like to work on this issue if nobody else is currently on it.

[mjcarroll]

@jan10010 Excellent! I will assign this to you. If you run into any issues, please feel free to follow up here, or join us on zulip to chat there.

[jan10010]

I identified the following completers that need tests:

• ros2action: ActionTypeCompleter, ActionGoalPrototypeCompleter
• ros2component: ComponentTypeNameCompleter
• ros2topic: TopicNameCompleter, TopicTypeCompleter, TopicMessagePrototypeCompleter
• ros2node: NodeNameCompleter
• ros2service: ServiceNameCompleter, ServiceTypeCompleter, ServicePrototypeCompleter
• ros2run: ExecutableNameCompleter

I’m planning to implement the tests using the same approach as in #1172 (ParameterNameCompleter) and submit a single PR once everything is ready. If you’d prefer I split it into incremental PRs (per command/package), let me know and I’ll do that.

If I’m missing any completers you’d like covered, happy to update the list.

[fujitatomoya]

@jan10010 thanks! i am happy to review PR, let me know when it is ready!