Write a proper `rmw_take_sequence` test

[clalancette]

While investigating the causes behind ros2/rmw_cyclonedds#279 , we discovered that there is no test within ROS 2 that actually does a rmw_take_sequence and then checks on the results. We do have a test that is pretty close: https://github.com/ros2/rcl/blob/7a25a74cf911840224fb5b992d118c22c825f961/rcl/test/rcl/test_subscription.cpp#L388 . That initializes the sequence, fills it with messages, and then calls rcl_take_sequence.

It would be nice to have another variant of this test in this repository which specifically deals with rmw_take_sequence.

[Aswin0305]

Hi maintainers 👋,

I’m new to ROS 2 and open-source contributions, and I’m looking for a well-scoped first issue to work on and learn more about RMW behavior and testing.

I came across this issue (#176) and wanted to check whether it is still relevant and available to be worked on. If so, I’d be happy to take it up.

Are there any pointers on where to start (e.g., existing tests to look at, expected behavior, or preferred rmw implementations to target)?

Thanks for your time!