The instrument, not the tests, was the bottleneck. Coverage is now
(PS4-traced lines | kcov hits) & (kcov line set - continuation lines).
The trace deliberately does NOT supply the denominator. A trace reports only
lines that RAN, so using it for both halves would make every subject 100.00%
and arm a repo-wide gate that checks nothing.
Three measured findings, each of which yields a silently wrong trace:
1. kcov's ptrace and bash's xtrace cannot share a process. Under
SHELLOPTS=xtrace every line kcov recorded as hits="1" comes back hits="0"
-- reproduced A/B on one subject. Hence two passes, two namespaces.
2. SHELLOPTS is readonly inside bash, so `export SHELLOPTS=xtrace` fails and
tracing never turns on; and `set -x` does not reach child processes.
3. Decisive: bash under `unshare --map-root-user` runs PRIVILEGED and
DISCARDS an inherited PS4, falling back to "+ " while still honouring
xtrace. The trace loses its file:line prefix and every subject reads 0%.
Fixed by delivering PS4 and `set -x` through a BASH_ENV file, which also
solves child-process propagation.
A fourth trap, in the report: kcov records filename="dwm_config.sh", a bare
basename. The source path comes from the trace's ${BASH_SOURCE} or a unique
repo search; an ambiguous basename yields no exclusion rather than a guess.
Measured through run_all.sh, nothing down:
dot_resolver_install.sh 39/39 = 100.00% (acceptance, unchanged)
rpi_nc_ca.sh 73/73 = 100.00% (was 72/73 = 98.63%)
dwm_config.sh 65/66 = 98.48% (was 35/73 = 47.95%)
rpi_nc_install.sh 85/88 = 96.59% (was 10/88 = 11.36%)
rpi_nc_ca reaching 100% is the load-bearing check: its missing line 141 was
cross-process contagion, and the trace pass has no kcov in it to contaminate.
dwm_config's remaining line 39 is a `done < <(...)`. Left in the denominator
on purpose -- removing lines inflates coverage, the fail-open direction, so a
second exclusion rule needs per-line justification, not a pattern from one lib.
Both new Python modules hold 100% branch coverage (29 tests).
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
The jail recorded each case's exit code but reported only timeouts,
discarding every other non-zero status. A suite with a failing assertion
exited 0 through the push gate -- the same blind spot that let an earlier
session ship 2 failing assertions in the nc_php suite. Found by negative
control, not by reading: a deliberately failing assertion still exited 0.
Propagating that status unconditionally was wrong, and caught before landing:
the jail's own usage example passes a `bogus` case that exits non-zero to
cover an error path, so a clean 5/5 = 100.00% run started failing. That is
the mode the 105-lib campaign runs in.
So the behaviour sits behind --fail-on-case-error, default off, passed only
by ci_mirror.sh and shell-tests.yml. Verified in all four quadrants:
measurement + error case = 0, gate + error case = 1, gate + clean suite = 0,
gate + broken assertion = 1.
Both gates also pass --min 0: with no --measure the jail was measuring
run_all.sh itself against its default --min 100 and failing the push at
54.55%, a coverage verdict neither gate asked for. ci_mirror.sh now prints
the jail's output on failure, so a red gate can be diagnosed.
The added flag pushed the jail over the 250-line cap, so the in-namespace
case runner moved to lib/shell_coverage_case_runner.sh, following the
existing lib/shell_coverage_jail_setup.sh split. All four quadrants were
re-run after the extraction.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016sxxsDHWgdRhmdmzNMA6XM
