Add test/[ alphabet matrix (mix bash_fixtures.gen test)

[davydog187]

Implements #70 item 2 for test / [ only: a generated test_matrix suite in the same generate / record / test path as date_matrix and printf_matrix.

This is not the item-3 filesystem-shape × command cube (~480 cells). Operators are crossed with revealing operand shapes for that operator so padding/boundaries/false-vs-missing stay visible — the date lesson — without enumerating every FS command.

What was enumerated

mix bash_fixtures.gen test writes 246 cases:

• Full POSIX/[ operator list on test: -b -c -d -e -f -g -h -k -L -n -p -r -S -s -t -u -w -x -z, = == != < >, -eq -ne -lt -le -gt -ge, -nt -ot -ef, -a -o, !, plus bash extras -G -O -N
• File operators × file / empty / dir / missing / symlink / dangling, plus chmod'd, fifo, /dev/null, trailing-slash and ENOTDIR boundaries
• -z/-n and one-arg forms at empty / hi / 0 / space (and operator-as-operand)
• String and integer compares at two or more pairs per family so one value cannot hide the bug (hi/hi vs a/b, 0/1 vs 10/9)
• Both test and [ on a representative subset (-e/-f/-d/-L/-s, -z/-n, =/!=, -eq/-lt, !, one-arg) so the two spellings cannot drift
• Syntax cells: no args, extra args, unknown operators, missing ], grouping

mix bash_fixtures.gen test --dry-run reports test_matrix: 246 cases. mix bash_fixtures.gen now generates date, printf, and test.

Recording

Docker was not available on the agent VM. Oracle output was recorded with the same test/fixtures/runner.sh the Docker task runs, under GNU bash 5.2.21 / Ubuntu 24.04 (uid ubuntu, not root — so chmod 000 permission cells are meaningful), then pretty-printed through Mix.Tasks.BashFixtures.write_json!/2:

mix bash_fixtures.gen test
bash test/fixtures/runner.sh < test/fixtures/bash_cases/test_matrix.json > /tmp/test_matrix_raw.json
# then Jason-pretty-print + Fixtures.validate, as `mix bash_fixtures` does

To re-record through Docker when it is available:

mix bash_fixtures test_matrix

Known gaps (44 of 246)

No cell was omitted. Divergences are opts.known_gap (excluded from the digest). The fixture runner still executes them with the assertion inverted.

Count	Reason
6	-r/-w/-x are existence checks; bash tests the permission bit (-x on a 644 file, -r/-w on chmod 000)
6	Leading-space integer operands ( 7) — Integer.parse/1 rejects them
6	Non-numeric -eq family: JustBash exits 2 with no diagnostic; bash writes stderr
4	Cannot construct fifo / setuid / sticky / dated-mtime shapes, and/or the operator is unimplemented
4	-nt/-ot/-ef unimplemented (revealing true side: newer-than, older-than, same-file, hardlink)
3	[ without a closing ] still evaluates; bash exits 2
3	( ) grouping unimplemented
2	/dev/null typed as a regular file; bash reports a character device (-f, -c)
2	Extra / too-many arguments: exit 1 vs bash exit 2 + diagnostic
2	Unknown operator (-Z, -xx): exit 1 vs bash exit 2 + diagnostic
2	-O/-G unimplemented (true on a file we own)
1	Directory size 0 so test -s dir is false
1	Trailing slash on a regular file treated as the file; bash requires a directory
1	Unary -a is not a synonym of -e
1	4-arg -f file -a -d dir is not expression AND/OR

JustBash.exec/2 did not raise on any cell. No test/[ implementation bugs were fixed in this PR — it is the enumeration + harness.

Cheap follow-ups the matrix now makes un-skippable

• -x/-r/-w should consult mode bits, not existence
• -c / character-device type for /dev/null (and stop reporting it as -f)
• -nt/-ot/-ef
• [ missing-] and unknown-operator diagnostics (exit 2)
• Integer operands: leading spaces, and a stderr diagnostic on non-numeric
• Unary -a as -e; 4-arg -a/-o as expression AND/OR
• Directory size so test -s dir is true

Not in this PR: the item-3 FS-shape × command cube, Oils activation, CI topology changes.

Tests

All local quality gates passed:

• mix compile --warnings-as-errors
• mix format --check-formatted
• mix credo --strict (only the existing intentional banned_fixture_apply finding)
• mix dialyzer (zero new errors)
• mix test — 6346 tests, 0 failures
• mix test --only suite:test_matrix — 246 tests, 0 failures
• mix bash_fixtures.gen test --dry-run — test_matrix: 246 cases

Related Issues

Related to #70 (item 2, test/[ only; not closing the issue)

Type of Change

• New feature (non-breaking change which adds functionality)

Testing

• Added new tests
• All existing tests pass
• Tested manually (mix bash_fixtures.gen test --dry-run, local runner.sh recording, JustBash vs oracle classification)

Checklist

• My code follows the style guidelines of this project
• I have run mix format
• I have run mix credo and addressed any issues
• I have added tests that prove my fix is effective or that my feature works
• New and existing tests pass locally with my changes
• I have updated the documentation accordingly
• I have updated the CHANGELOG.md (for non-trivial changes)