testRTC is configured to terminate a test automatically after 5 minutes.
This is why if you try to run a long test, it will fail with this error message.
To resolve the issue, add #timeout:XXX to the run options of the test, where XXX stands for the number of minutes you want to allow.
Typically, for long tests and/or stress tests, we recommend timeout to be set to 5 to 10 minutes more than the expected test time.
Note that the timeout is set for every iteration.
The above example gives you up to 10 minutes for the test before it will be terminated.