Keep semaphore slots held while blocked jobs are enqueued in concurrency test

[wintan1418]

Related to #602

Problem

ConcurrencyControlsTest#test_run_several_jobs_over_the_same_record_limiting_concurrency is one of the most frequent CI flakes at the moment — it failed standalone on recent main runs (e.g. the run for 7f59932) and on unrelated PR runs, always on the same assertion:

Expected: 5
  Actual: 4  # BlockedExecution difference

The test claims all three semaphore slots with jobs A, B and C, waits until the three are claimed, then enqueues D–H expecting all five to become BlockedExecution. A and B only pause for 0.5s — and that clock starts as soon as they're claimed, before the wait even returns. On a slow runner, by the time the five D–H perform_later inserts complete, A or B has already finished and released a semaphore slot, so one of D–H claims it instead of blocking, and the +5 assertion comes up short.

Fix

Give A and B enough pause (1.5s) to still be holding their slots while D–H are being enqueued, and bump C (3s → 4s) so it keeps finishing well after everything else, preserving the test's final ["C"] assertion. The constraint is now also documented in the test comment.

Adds ~1s to the test's runtime in exchange for tripling the margin on the race window.

Testing

Ran the test 6 consecutive times on MySQL plus the full concurrency_controls_test.rb file — all green.

[rosa]

Thanks @wintan1418! These tests are quite flaky and tricky to get right... I might rewrite all of them at some point 😅

[wintan1418]

IKR, thanks.

…

On Tue, Aug 18, 2026 at 6:49 PM Rosa Gutierrez ***@***.***> wrote: Merged #776 <#776> into main. — Reply to this email directly, view it on GitHub <#776?email_source=notifications&email_token=AOPBFMR72WQ6EZIA7ISBHKD5KSJKFA5CNFSNUABQM5UWIORPF5TWS5BNNB2WEL2JONZXKZKFOZSW45CON52GSZTJMNQXI2LPNYXTEOJWGM2TSMZYG43TRJTSMVQXG33OU5WWK3TUNFXW5JLFOZSW45FMMZXW65DFOJPWG3DJMNVQ#event-29635938778>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AOPBFMUA7LDU3IXYENOL25L5KSJKFAVCNFSNUABFKJSXA33TNF2G64TZHM2TQOBVGA4DQNJWHNEXG43VMU5TKMBRHE3DMMJSHEZ2C5QC> . Triage notifications, keep track of coding agent tasks and review pull requests on the go with GitHub Mobile for iOS <https://github.com/notifications/mobile/ios/AOPBFMSYXR5MHAJVGZM2JGL5KSJKFA5CNFSNUABQM5UWIORPF5TWS5BNNB2WEL2JONZXKZKFOZSW45CON52GSZTJMNQXI2LPNYXTEOJWGM2TSMZYG43TRJTSMVQXG33OU5WWK3TUNFXW5JLFOZSW45FKMZXW65DFOJPWS33T> and Android <https://github.com/notifications/mobile/android/AOPBFMUV3JUGBXFNTYBIT5L5KSJKFA5CNFSNUABQM5UWIORPF5TWS5BNNB2WEL2JONZXKZKFOZSW45CON52GSZTJMNQXI2LPNYXTEOJWGM2TSMZYG43TRJTSMVQXG33OU5WWK3TUNFXW5JLFOZSW45FOMZXW65DFOJPWC3TEOJXWSZA>. Download it today! You are receiving this because you were mentioned.Message ID: ***@***.***>