Gtest concept for ROS2 foxy

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Hello! i'm new in using ROS2 foxy.

i want to test a macro actions node which contains publishers and subscribers for my robot actions. Each action is written as a method such as stopMotion(), GoToPosition() , i want to know if there is a way to test those methods like: if i give 0 to the request action stopmotion willl set zeros for the velocities and the commands. i don't know how to write this as a test node and i'm not sure if i understood the concept of gtest and test launch.

Does gtest only check if the node is running or the behave of the node like the example i gave