DefaultUnderATimeLimitReturnsAValidPlanNoWorseThanUnlimited failed on CI
(runs 41219924107 and 41224809174, Engine.Tests job): the fixed 5 s limit
assumed the unlimited Default solve takes well under a second, but it takes
about 4 s locally and longer on a loaded runner. A limit shorter than the
normal Irregular search correctly returns an earlier, worse plan, so the
assertion only holds when the limit covers that search. Use the larger of
5 s and three times the measured unlimited solve.
Red: the old test fails on one CPU shared with three busy loops; the new
one passes there. Full Engine.Tests: 2780 passed, 2 skipped.