continuous_single_target_interruption_drains_final_events_and_succeeds
intentionally allows SIGINT as soon as the fake server has sent its
reply, even if the managed client hasn't consumed it yet. The
echo_reply assertion is what proves shutdown drains a still-queued
reply instead of losing it; gating on client-side consumption would
remove the in-flight scenario the test exists to cover.
Nils Andreas Svee