Added README for updown test

nav2_system_tests/README.md

@@ -29,5 +29,8 @@ Test the integration of several components and subsystems.
 - Command chain (Mission Planning, Mission Execution, Navigation System, Robot Interface)
 
 ## 3. System Testing
+Test the lifecycle startup and shutdown of nodes.
+ - [Updown Test](src/updown/README.md)
+
 Test the integration of all subsystems.
  - [System Test](src/system/README.md)

nav2_system_tests/src/updown/README.md

+# Navigation2 Updown Test
+
+This is a 'top level' system test which tests the lifecycle bringup and shutdown of the system. 
+
+## To run the test
+```
+ros2 launch nav2_system_tests test_updown_launch.py
+```
+
+If the test passes, you should see this comment in the output:
+```
+[test_updown-13] [INFO] [test_updown]: ****************************************************  TEST PASSED!
+```
+
+To run the test in a loop 1000x, run the `test_updown_reliablity` script and log the output:
+` > ./test_updown_reliablity |& tee /tmp/updown.log`
+
+When the test is completed, pipe the log to the `updownresults.py` script to get a summary of the results:
+` > ./updownresults.py < /tmp/updown.log`
+