With colors being true but long and verbose being false, the output of run_tests_main is somehow strange. Here is the captured output with control characters being escaped (except for line feeds). For some reasons, random was repeated.

^[[2K^Mrandom seed: 356596957^[[0m^M
^[[2K^Mrandom================================================================================^[[0m^M
^[[2K^Mrando;32;1msuccess^[[0m (ran 12 tests)^M

I have tried different shells and terminal emulators, and the behavior seems to be the same.