The mutation pass turned up one defect that did not make the suite go
red: a reader branch that forgets to advance reads the same character
for ever, and dune test waits as long as it is left to. In CI that is a
job killed by the runner with nothing named and no output to read.
watchdog.ml puts an alarm on every test binary — generous, because an
alarm that fires on a slow machine is a flake — and a five-second one
around each read in test_flan, where the budget really is small. The
first read that does not return wedges the rest, so a looping reader
costs five seconds and names the row instead of costing eight minutes
or never finishing. Both were watched: the string-escape loop now fails
in five seconds with the case named, and the per-binary backstop was
armed short and observed to fire.
Joseph Ferano
3ace7c262f