Phase 4.6: Viewer round-trip tests (inferno SVG render + speedscope folded import) - #16
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…ase 4.6)
- snmalloc-rs/Cargo.toml: add `inferno = "0.11"` as a dev-dependency
(test-only; never appears in the published crate's transitive deps).
Version pin documented inline -- 0.11 keeps MSRV aligned with the
rest of the workspace, while later 0.12.x bumps `rust-version` to
1.71 and pulls in additional crossbeam transitive deps we don't
otherwise need.
- snmalloc-rs/tests/profile_viewer_roundtrip.rs: new integration suite
asserting that the folded-stack output emitted by Phase 4.3's
`HeapProfile::write_flamegraph` is consumable by two real viewers
in the Rust profiling ecosystem. Test-only -- no public API on
`HeapProfile` / `SnMalloc` is added, and `src/profile.rs` is not
touched.
* inferno_roundtrip -- captures a >=50-sample snapshot, writes its
folded form into a `Vec<u8>`, hands it to `inferno::flamegraph
::from_reader` with `Options::default()`, and asserts the
rendered SVG contains a `<svg` root and at least one `<g`
stack-frame group node. Confirms the round-trip from folded
bytes to SVG works without any post-processing.
* speedscope_folded_import -- re-implements the regex
`^([^\s]+) (\d+)$` that speedscope's "Brendan Gregg's collapsed
stack format" importer uses (per its wiki) and asserts >=95% of
folded lines match. speedscope itself runs in a browser/wasm
context we can't drive in CI, so the conformance check is the
next best thing.
* round_trip_weight_invariance -- regression guard for the Phase
4.3 BTreeMap collapse step: sum of folded weights over a
real-workload snapshot must equal
`HeapProfile::total_allocated_bytes` exactly.
* empty_snapshot_viewer_safety -- runs in both feature
configurations (no `#[cfg(feature = "profiling")]` gate).
Confirms `write_flamegraph` on an empty profile writes zero
bytes and that inferno cleanly returns `Err` rather than
panicking when handed the resulting empty stream. Covers the
OFF-build path where every snapshot is empty by construction.
- Workload calibration: 5_000 x 64-byte allocations at sampling
rate 512 -> ~625 expected samples (well above the 50-sample floor
Phase 4.6 requires). Smaller than the 100k workload in
profile_accuracy.rs to keep CPU contention low when `cargo test
--all --features profiling` runs the two test binaries in
parallel. Workload-driving helpers live in a
`#[cfg(feature = "profiling")]` module to avoid dead-code warnings
on the OFF build.
Verified:
- cargo test --all (profiling OFF): all binaries green, including
the new profile_viewer_roundtrip binary running just
empty_snapshot_viewer_safety.
- cargo test --all --features profiling: stable across 5
back-to-back runs; all 4 new tests pass, all pre-existing tests
pass.
- cargo test --features profiling --test profile_viewer_roundtrip:
4 passed, 0 failed.
- No new compiler warnings in either feature configuration.
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Summary
Tests-only addition validating
write_flamegraphoutput is consumable by real viewers. No public API changes.inferno::flamegraph::from_reader, asserts<svg+ at least one<gelement^([^\s]+) (\d+)$regex (without pullingregexcrate), asserts ≥95% of folded lines matchAdded
inferno = "0.11"as dev-dependency (pinned for MSRV alignment).Test plan