Since the testsuite script and its configuration file are committed, I think it would be a good idea to also change the (hardcoded) default value of GRASSSRC from:
source code directory as full path:
GRASSSRC=“$HOME/software/grass77”
To something like:
GRASSSRC=“$(cd …/…/; pwd)”
GRASSSRC=“$(realpath …/…/)”
So that you don’t need to necessarily edit them in order to run them