majiayu000 ROS 2 Testing, Rosbag2 & Tracing Instructions (Ubuntu 24.04 LTS & ROS 2 Jazzy)
1. Documentation Entry Points
| For | Entry point |
|---|---|
| Testing tutorials (CLI, gtest, pytest, integration) | https://docs.ros.org/en/jazzy/Tutorials/Intermediate/Testing/ |
launch_testing / rosbag2_cpp / rosbag2_py API |
https://docs.ros.org/en/jazzy/p/<package>/ |
| rosbag2 source of truth | https://github.com/ros2/rosbag2 |
2. Running Tests
colcon test only prints a summary, so read results with colcon test-result --all --verbose — without --verbose you cannot see which case failed, and a test that was never registered with the build looks identical to a passing one, so confirm the expected test count rather than the exit code.
3. Key Concepts & Code Patterns
A. Programmatic Rosbag2 Writer (C++)
#include <rosbag2_cpp/writer.hpp>
#include <std_msgs/msg/string.hpp>
rosbag2_cpp::Writer writer;
writer.open("my_bag");
writer.create_topic({0, "chatter", "std_msgs/msg/String", "cdr", {}, ""});
writer.write<std_msgs::msg::String>(msg, "chatter", clock.now());
B. Integration Testing (launch_testing Python)
In generate_test_description(), return a LaunchDescription ending in launch_testing.actions.ReadyToTest() — everything before it is launch setup, plain unittest.TestCase classes run after it against the live processes, and @launch_testing.post_shutdown_test() classes run once the processes have exited (where launch_testing.asserts.assertExitCodes(proc_info) belongs).
4. Symptom -> Root Cause -> Action
| Symptom | Likely root cause | Action |
|---|---|---|
| Node under test never receives the test publisher's messages | QoS mismatch between test fixture and node — same silent DDS failure as production | Match the node's QoS in the fixture; see ros2-troubleshooting (check_qos_compat.py) |
| Rosbag2 playback in a test produces no callbacks | Bag recorded with use_sim_time semantics but the test runs on wall clock, or /clock not published during playback |
Align use_sim_time across the test nodes; play with --clock when the bag drives time |