The pipeline backpressure integration tests in tests/integration/test_pipeline_memory_backpressure.rs size their input via a FAMILIES constant. During the 2026-08-16 review sweep, the read-ahead margin was measured at ~2.46 MiB sitting just under input_len / 2 (~2.7 MiB) — limited headroom. A future toolchain or dependency change to BGZF block sizing could materially shift how much the reader buffers and break the margin, making these tests flaky or wrong.
The most brittle assertion (settled.bytes < input_len / 2 in stalled_writer_stops_the_reader_within_the_queue_memory_budget) was already made budget-relative (unread >= TEST_BUDGET_BYTES) as part of PR #764's coverage fix. This issue tracks the remaining hardening: make the fixture sizing / any remaining fraction-based margins robust to BGZF block-size drift rather than relying on the current tight headroom.
Task
- Audit
FAMILIES/fixture sizing and every margin assertion in test_pipeline_memory_backpressure.rs.
- Make margins budget-relative (assert the reader left ≥ one budget unread) or size the fixture with clear headroom, without regressing the llvm-cov coverage-job runtime (the fixture was deliberately shrunk to avoid a >120s timeout — don't reintroduce that).
Placement note
The fixture and these tests are introduced by PR #764 (branch 746/nhomer/bound-consensus-memory-under-writer-stall) and are not in main yet. The fix therefore belongs in #764 (folded into that PR), not a separate branch off main. This issue exists for tracking; link it from #764.
Notes
The pipeline backpressure integration tests in
tests/integration/test_pipeline_memory_backpressure.rssize their input via aFAMILIESconstant. During the 2026-08-16 review sweep, the read-ahead margin was measured at ~2.46 MiB sitting just underinput_len / 2(~2.7 MiB) — limited headroom. A future toolchain or dependency change to BGZF block sizing could materially shift how much the reader buffers and break the margin, making these tests flaky or wrong.The most brittle assertion (
settled.bytes < input_len / 2installed_writer_stops_the_reader_within_the_queue_memory_budget) was already made budget-relative (unread >= TEST_BUDGET_BYTES) as part of PR #764's coverage fix. This issue tracks the remaining hardening: make the fixture sizing / any remaining fraction-based margins robust to BGZF block-size drift rather than relying on the current tight headroom.Task
FAMILIES/fixture sizing and every margin assertion intest_pipeline_memory_backpressure.rs.Placement note
The fixture and these tests are introduced by PR #764 (branch
746/nhomer/bound-consensus-memory-under-writer-stall) and are not inmainyet. The fix therefore belongs in #764 (folded into that PR), not a separate branch offmain. This issue exists for tracking; link it from #764.Notes
reports/2026-08-16-retro.md, item Bump tempfile from 3.23.0 to 3.24.0 #7).