Update README for using ctest_loop script

nav2_system_tests/src/system/README.md

@@ -3,23 +3,40 @@
 This is a 'top level' system test which will use Gazebo to simulate a Robot moving from an known initial starting position to a goal pose. 
 
 ## To run the test
-First, build the package
+First, remove the COLCON_IGNORE; this exists so the system tests won't be in the debian release package
+```
+rm nav2_system_tests/COLCON_IGNORE
+```
+Then, you must build navigation2 including this package:
 ```
 colcon build --symlink-install
 ```
-Then you can run the test:
+Then you can run all the system tests:
 ```
 colcon test --packages-select nav2_system_tests
 ```
 Output results will go to the screen, and will be logged to the "log/latest_test/nav2_system_tests/" path relative to where colcon test was run.
 
-## Notes: (Dec 18 Crystal release)
+To run just the bt_navigator test:
+```
+cd build/nav2_system_tests
+ctest -V bt_navigator$
+```
+
+To loop over the bt_navigator test, a script has been provided:
+```
+nav2_system_tests/scripts/ctest_loop.bash -c <# loops> -o <path/to/summary/filename.txt> -l <path/to/store/failing/logfiles.log> -d <dds to use>
+```
+
+Example (loop 100 times using fastrtps):
+```
+nav2_system_tests/scripts/getopt_ctest_loop.bash -c 100 -o /home/robot/data/results.txt -l /home/robot/data/results.log -d rmw_fastrtps_cpp
+```
+
+## Notes: (updated Aug 2019)
  * This currently uses a turtlebot3 robot model, world and map.
  * The test normally takes 1-2 minutes to run, with a timeout of 2 minutes
- * Due to current issues with the Navigation2 initialization, the bringup can sometimes require a retry, so the test automatically internally retries sending an initial pose and goal pose if it doesn't reach the goal within a default 30 second time from when the goal pose was sent
- * The test is currently using the 'simple_navigator' controller
- 
+
 ## Future Work
- * Add an additional test for the 'bt_navigator' controller
  * Add additional goal poses if the first one successfully passes
- * Remove the dependency on the turtlebot3 model and map by adding a simple / dummy robot and creating a world and map
\ No newline at end of file
+ * Remove the dependency on the turtlebot3 model and map by adding a simple / dummy robot and creating a world and map