The min_size=10 default survived to 1.2.4 because every PG test injected a
pool and thus skipped the pool-building path entirely. Unit tests now assert
the create_pool arguments, but "we passed min_size=0" and "the server really
opened that many backends" are two different claims, and only a real instance
can settle the second one. Count via a run-unique application_name carried on
the DSN: the instance is shared with other projects, so counting by database
or role would fold their connections into ours and make the case flaky by
construction.
Degradation is exercised through an unreachable DSN rather than by exhausting
the shared instance's connections. A refused connection lands in the same
class as exhaustion, and the fake clock lets the 60s cooldown be observed
without sleeping. retry_after_s is the signal that separates a real retry
(which renews the window) from the cheap short circuit (which does not).
Evidence: with create_pool reverted to its pre-fix form both cases go red
(observed 10 backends after a single write, and refusal surfacing at pool
creation instead of at prepare time).
iomgaa
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