# G-092 Split long-running test files to lower the parallel floor of broad runs

Status: proposed
Scope: src/tests/modules/punk/mix/testsuites/scriptwrap/ (multishell.test), src/tests/shell/testsuites/binscripts/ (dtplite.test), src/tests/modules/argparsingtest/testsuites/argparsingtest/ (argparsingtest.test), src/tests/shell/testsuites/punkexe/ (scriptexec.test - if assessed worthwhile), src/tests/runtests.tcl (longest-first weight table), src/tests/AGENTS.md + affected child AGENTS.md
Goal: no single monolithic test file dominates the -jobs parallel critical path: the long-running suites are split into cohesive smaller files (grouped along shared-fixture boundaries, every test preserved verbatim) so a broad -jobs 8 run's slowest child process is bounded by its slowest cohesive test group rather than a whole legacy file.
Acceptance: after the split, repeated -jobs 8 full-suite runs on the reference machine report no child process wall above 45s in the runner's slowest-child listing and improve full-suite wall time by at least 25% versus the G-091 verification baseline (2m16s); test conservation is proven and recorded in this file - global tallies identical to a pre-split sequential baseline and the full set of test names unchanged (name-level comparison, mechanism decided in the work - e.g. a names mode for scriptlib/developer/runtests_parity.tcl); no test is deleted, skipped, weakened, or renamed, and provenance comment lines travel with moved tests; the runtests longest-first weight table covers the new files; scriptlib/developer/runtests_parity.tcl reports PARITY ok between -jobs 8 and -jobs 1 on the split tree; affected AGENTS.md contracts (src/tests + shell/binscripts and scriptwrap references) are updated.

## Context

G-091's verification (2026-07-19, archived - goals/archive/G-091-runtests-parallel-jobs.md)
established the floor anatomy with per-child WALL measurements (the runner now prints them;
child wall includes boot and file-level fixture cost that per-test usec misses):

- multishell.test child: ~2m wall (85s summed test time - the two ~30s roundtrip/checkfile
  tests plus two ~11s wrap tests - the remainder boot + shared scriptwrap fixtures). This
  single child IS the current -jobs floor: full-suite -jobs 8 wall 2m16s.
- dtplite.test ~25s (two ~12s tests), argparsingtest.test ~27-30s (largest single test
  7.8s), scriptexec.test ~10-11s. Everything else is small.
- Post-split ceiling estimate: total child work ~330s / 8 workers ~41s, serial tail ~16s,
  slowest single test ~32s (scriptwrap_runtime_cmd_roundtrip_no_drift) + child boot ~3s ->
  slowest child ~35-40s, full-suite wall ~65-80s expected (acceptance leaves headroom for
  the ~30s run-to-run machine variance observed during G-091).

Split considerations gathered in the same session:

- Fixture duplication tradeoff: multishell's namespace-level fixtures are shared by all its
  tests; each new file re-pays fixture setup and child boot, so total CPU rises as wall
  falls. Split along fixture boundaries (tests sharing a fixture stay together) to bound
  the duplication; the tradeoff is accepted by this goal's premise (wall time of broad
  parallel runs is the optimisation target).
- exec.test is excluded: it is imported/adapted Tcl core material (src/tests/core contract
  preserves upstream compatibility intent) and its child is only ~5s.
- src/tests contracts that bind the work: do not delete, skip, or weaken tests; provenance
  comment lines are immutable facts that must move with their tests; child AGENTS.md files
  name multishell.test and dtplite.test in their contracts and need corresponding updates.
- The runtests longest-first weight table (static globs in runtests.tcl) references the
  pre-split filenames and must be updated with measured weights for the new files.
- None of the split candidates are in the -serial-paths default, so the serial tail is
  unaffected.

## Notes

- Complementary, independent: the lean-children candidate (explicit package requires for
  the 17 preload-dependent files so children can drop the shellrun preload + runx warmup)
  reduces the per-file boot cost that splitting multiplies - doing it first or alongside
  lowers the split's total-CPU cost. Recorded in goals/archive/G-091 notes.
- Related: G-029 (packaged test::<modulename> modules built from src/tests) consumes this
  tree as its source of truth - file granularity changes flow into that packaging design.
- The 45s child-wall criterion is the noise-robust metric (child walls were stable across
  runs while full-suite wall varied up to ~30s); the 25%-vs-2m16s wall criterion is
  relative to the same-machine G-091 baseline rather than an absolute number for the same
  reason.