Capture errset stdout into a variable

Good evening, I'm attempting to make a "function linter" to run a couple generic test cases through a function to ensure it succeeds a baseline.

My current workflow is running them through an errset. I see that errset has a t/nil property for printing the error, but I need access to the actual error string. Is there a solid way to redirect the stdout into a variable? I can see redirecting it into a file and reading it into a variable but that route seems erroneous. 

Example:
procedure(test(x) unless(x == 1 error("generic error"))
res = errset(apply('test list(2)) t)
prints: *Error* generic error


Thanks, Trevor