How to use launch_testing for testing executables created by cpp ros2 nodes?

edit

You can use launch_ros for both cpp nodes and python nodes i guess for. For python you have to use the setup.py to make necessary files available to the test and for cpp the CMakeList.txt.

Below is the code you have to add to your CMakeList if testing a cpp package and the launch description for the node that is to be tested:

In your CMakeList.txt include

install(FILES
  test/<name>_launch_testing.py
  DESTINATION lib/${PROJECT_NAME})

if(BUILD_TESTING)
   find_package(launch_testing_ament_cmake)
  add_launch_test(test/<name>_launch_testing.py)
  find_package(ament_lint_auto REQUIRED)
  ament_lint_auto_find_test_dependencies()
endif()

Your generate_test_description(): inside <name>_launch_testing.py then gives your cpp node to the test system:

dut = Node(
    package='ros2_cpp_test_example',
    executable='<name>',
    name='<name>',
)
context = {'dut': dut}

return (launch.LaunchDescription([
    dut,
    launch_testing.actions.ReadyToTest()]
    ), context
)

Below the launch description you can add your testcases using the class unittest.TestCase. You can access the output of the launched nodes as described in the links you supplied.

Inside the testcases you can also start a testnode that receives/sends messages of/to the node you want to test as shown in https://github.com/ros2/launch_ros/bl...

Here you can find an example package in addition to the official documentation with Ubuntu 20.04 and Foxy: https://github.com/GitRepJo/ros2_cpp_...