[bfs2021]

Problem

In the Alpine (test-alpine) CI job and in the official bash:* images, every UTF-8 test skips: the summary shows 26 locale skips plus check-posix-compat.sh ... skipping because ShellCheck isn't installed, so CI reports 0 failures without having run the coverage that matters most on musl (the 3.0 BusyBox script-name bug appeared exactly there).

Fixes #152 (all four proposed fix steps from the issue are covered here)

Root cause

The test helpers discover a UTF-8 locale with locale -a. musl ships no locale utility, so the lookup returns nothing even though musl supports C.UTF-8 (and accepts every other locale name) without installed locale files — musl's default since 1.1.11 in 2015. The Alpine job also never installs ShellCheck.

Fix

• Shared helper musl_c_utf8 in tests/test_helpers.sh: returns 0 on any musl system, by matching the ldd --version banner. musl's ldd prints the banner on stderr and exits 1, and run_tests.sh runs with pipefail, so the banner is captured first and the probe's status comes from grep alone (a plain pipeline always returns 1 under pipefail). No version floor: C.UTF-8 has been musl's default since 1.1.11 (2015), and a banner without a Version line can no longer change the result.
• One shared utf8_locale_name in tests/test_helpers.sh holds the candidate loop plus the musl C.UTF-8 fallback; the copies in test_posix_compat.sh are gone. equivalence_utf8_locale (test_validator_equivalence.sh) keeps only the Linux-only check at the equivalence call site and delegates to the shared helper.
• compat_locale_available (test_shell_compat.sh) routes its C.UTF-8 case through the shared helper; other names stay unavailable since musl only speaks UTF-8.
• test_posix_levels_in_turkish_locale stays skipped on musl, with a reason: musl has no locale-specific case mapping, so tr_TR.UTF-8 behaves like C.UTF-8 and the test would pass even with the LC_ALL=C guard around the tr case mapping in logging.sh removed. Other systems keep the locale -a check.
• New TEST_MAX_SKIPPED guard in run_tests.sh: when set, a run that skips more tests than the threshold fails. The test-alpine job sets TEST_MAX_SKIPPED=10 (the 5 intentional skips plus 5 Turkish-locale skips), so a future change cannot silently skip coverage again.
• The test-alpine job installs shellcheck so check-posix-compat.sh runs there too.

Testing

In alpine:latest, non-root like CI, with the test-alpine job's command (TEST_SHELLS="bash,bash --posix,zsh,dash,busybox sh" TEST_REQUIRE_SHELLS="zsh dash busybox" plus TEST_MAX_SKIPPED=10):

• Before: Total Tests: 907, Passed: 875, Failed: 0, Skipped: 32 — 26 locale skips (no UTF-8 locale installed, locale C.UTF-8 is not installed, tr_TR.UTF-8 locale not installed, ...), plus shellcheck not installed.
• After: Total Tests: 907, Passed: 897, Failed: 0, Skipped: 10 — every UTF-8 test runs and passes on musl, including validators match validators_utf8.tsv and utf8_messages.sh matches bash. The 10 remaining skips are the 5 intentional ones plus the Turkish-locale test, now skipped on musl with its reason; TEST_MAX_SKIPPED=10 passes exactly at the threshold.
• Guard verified: TEST_MAX_SKIPPED=0 on a suite with skips exits 1 with Error: 2 tests skipped, exceeding TEST_MAX_SKIPPED=0; a non-integer value is rejected the same way.
• Non-musl systems are unaffected: on glibc locale -a still drives detection and musl_c_utf8 returns 1 (verified on Git Bash/MSYS, where locale -a lists C.utf8).

[GingerGraham]

Thanks for this @bfs2021 . The C.UTF-8 fallback works: the Alpine job goes from 32 skips to 5, and the
bash:* jobs no longer skip the UTF-8 tests. A few changes before merge. Fixes #152 will close
the issue, so anything from it that isn't done here needs to be done or split into a new issue.

1. Keep the Turkish locale test skipped on musl
#152, proposed fix step 3: "Leave the Turkish locale test skipped on musl: musl has no
locale-specific case mapping, so the test would pass without checking anything."

The test checks the LC_ALL=C guard around the tr case mapping in logging.sh. On musl,
tr_TR.UTF-8 behaves like C.UTF-8 (as the PR description says, musl accepts any locale name),
so the test passes even if that guard is removed. Please revert the change to
test_posix_levels_in_turkish_locale. A skip reason that says why would help, e.g.
"musl has no locale-specific case mapping".

2. Add the skip-count guard
#152, last paragraph: "Add a CI check that fails if the Alpine job skips more tests than an
agreed number, so a future change can't silently skip them again."

With item 1 done, the Alpine job should skip 10 tests (the current 5 plus 5 Turkish). A
threshold such as TEST_MAX_SKIPPED=10 in the test-alpine job would do it, checked in
run_tests.sh or a workflow step. Applying the same check to the bash:* jobs is optional.

3. Use one shared locale lookup
#152, proposed fix step 1: "Move the three copies of the locale lookup ... into one
utf8_locale_name helper in tests/test_helpers.sh."

The PR adds the musl fallback to each copy separately. utf8_locale_name and
equivalence_utf8_locale are the same loop, so please merge them into one helper in
tests/test_helpers.sh, with the Linux-only check kept at the equivalence call site.
compat_locale_available checks whichever locale a scenario names, so it can't be replaced.
Its C.UTF-8 case should still go through the shared helper.

4. Drop the musl version floor, or give a source for it
#152, proposed fix step 2: "Detect musl from ldd --version 2>&1, which prints musl." The
issue sets no version floor.

As far as I can tell, C.UTF-8 has been musl's default since 1.1.11 in 2015
(https://openwall.com/lists/musl/2015/08/30/9), so I can't find a reason for 1.2.4. Unless you
have a source for 1.2.4, a plain musl check is simpler. It also fixes an edge case: at the
moment, a banner that contains "musl" but has no Version line returns 0.

5. Commit and PR title
tests is a scope in our Conventional Commits rules, not a type. Please use
test(tests): run the UTF-8 suites on musl by falling back to C.UTF-8.

[bfs2021]

All five points are addressed in 5e23c83:

1. Turkish-locale test: reverted to skipping on musl, with the reason in the skip message ("musl has no locale-specific case mapping: the LC_ALL=C guard cannot be tested").
2. Skip-count guard: run_tests.sh now fails when skips exceed TEST_MAX_SKIPPED, and the test-alpine job sets TEST_MAX_SKIPPED=10 (verified: the run passes with exactly 10 skips, and a lower threshold fails with the count in the error).
3. One shared helper: the candidate loop and the musl fallback now live only in utf8_locale_name in tests/test_helpers.sh; equivalence_utf8_locale keeps the Linux-only check at the equivalence call site and delegates, and compat_locale_available routes its C.UTF-8 case through the shared helper.
4. Version floor dropped: musl_c_utf8 is now a plain musl check on the ldd --version banner (C.UTF-8 has been musl's default since 1.1.11, 2015), which also removes the dependence on a Version line being present.
5. Title: commit and PR retitled to test(tests): run the UTF-8 suites on musl by falling back to C.UTF-8.

With these in, all four proposed fix steps from #152 are covered by this PR, so Fixes #152 needs no split-off issue. Full alpine:latest run as non-root with the CI command: 907 tests, 0 failed, 10 skipped.