fix(test): Make jitter deterministic via config override in the flusher test - #69264
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Add a #[cfg(test)] jitter_override field to BillingAggregatorConfig so the flusher timing test can pin jitter to a known value (100ms), eliminating the non-deterministic timing race caused by rand::thread_rng() in pick_jitter(). The test_flusher_swallows_initial_tick_then_flushes_on_interval test was flaky (~21 failures over 36 days) because random jitter made the interval creation time unpredictable under paused tokio time.
The field needs to exist in non-test builds too since clippy runs with --all-targets (which enables cfg(test)) and config.rs constructs the struct outside of #[cfg(test)] modules. The field is #[doc(hidden)] and defaults to None with zero runtime cost.
…in mapping test - fix off-by-one-ms timing comments in test_flusher_swallows_initial_tick_then_flushes_on_interval (t=1101ms, not t=1100ms) - clarify the jitter is pinned, not a random range, in this test - assert jitter_override stays None in get_billing_aggregator_config_maps_fields_correctly
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July 9, 2026 19:28
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Summary
#[cfg(test)]jitter_overridefield toBillingAggregatorConfigsotest_flusher_swallows_initial_tick_then_flushes_on_intervalcan pin jitter to a known value (100ms), eliminating the non-deterministic timing racepick_jitterusesrand::thread_rng(), making the interval creation time unpredictable under paused tokio timeHow it works
With
jitter_override: Some(Duration::from_millis(100)), the flusher sleeps for exactly 100ms. Afteradvance(101ms), it wakes and creates the interval at t≈100ms. The first real tick fires at t=1100ms. The test advances to t=1099ms and asserts zero flushes — this now passes deterministically regardless of RNG state.Insight
https://app.mendral.com/insights/01KT4HT5VY3AR9V53KRG28G9N4
Note
Created by Mendral. Tag @mendral-app with feedback or questions.