erp5testnode runs test inside of:

/srv/slapgrid/slappartXY/srv/testnode

Since it runs SlapOS profile tests, they run services in:

/srv/slapgrid/slappartXY/srv/testnode/ZZZ/inst/test0-0/tmp/inst/

Shortening it to:

/srv/slapgrid/slappartXY/srv/t/ZZZ/inst/test0-0/tmp/inst/

minimises chance to reach limit of maximum path, often hit by sockets.