test(api): drop an assertion on who won a race with the drainer - #70
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RequestIsSafeUnderConcurrentPublishAndDrain asserted served > 0: that at least one of 20,000 request() calls found a value in the slot. The drainer in the same test is a tight loop emptying that slot, so the assertion is a statement about scheduling, not about the code under test. It passed 200 consecutive local runs and failed once in CI under the BDE allocators on a loaded runner. Nothing is lost. That request() returns a present value is pinned deterministically by RequestReturnsTheCurrentValueWithoutSubscribing, and the assertion this test exists for - requests_served + requests_denied equals the number of calls made - is unaffected by who wins the race. A test that reddens the build at random teaches you to ignore red.
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RequestIsSafeUnderConcurrentPublishAndDrainassertedserved > 0: that atleast one of 20,000
request()calls found a value in the subscriber's slot.The drainer in the same test is a tight loop emptying that slot, so the
assertion is a statement about scheduling, not about the code under test.
It passed 200 consecutive local runs and failed once in CI, under the BDE
allocators on a loaded runner:
A re-run with no code change went green, which is the definition of the
problem.
Nothing is lost
That
request()returns a present value is already pinned deterministicallyby
RequestReturnsTheCurrentValueWithoutSubscribingandRequestSeesTheLatestValueNotTheFirst. The assertion this test actuallyexists for,
requests_served + requests_denied == 20000, is unaffected bywho wins the race and still runs.
The test's own comment already said the right thing - "the exact value read is
whatever was current at that instant" - and then asserted otherwise on the
next line.
A test that reddens the build at random teaches you to ignore red.