Andrew Kesterson f8425b8729 Gate mutation testing on a measured score, not an inherited one ...

The threshold had been 80 against src/stdlib.c alone. There are three
more sources now and nobody had measured them, so that number was a
guess carried forward.

Measured: 72.3%, 188 of a 260-mutant sample from the 1701 the four
sources generate. Gate set to 65 -- a ratchet with headroom for the
runner and for the sample shifting as sources change, not a target.

A sample rather than the whole set, because 1701 rebuilds and test runs
is hours. --max-mutants samples by even index rather than at random, so
the same 260 run every time and the gate stays reproducible; sampling
all four files beats exhausting one of them, which is what this job did
before.

72.3% against the 89.6% reported at 0.1.0 is a change in denominator,
not a regression in the tests. That figure covered one 561-line file;
this covers four totalling 1716 lines, and most of the added surface is
argument validation whose mutants are frequently *equivalent* -- 12 of
the 72 survivors are `errno = 0` deleted from a wrapper whose libc call
always sets errno, which no test that could be written would catch. The
README breaks all 72 down and says which are worth acting on; TODO.md
2.4 carries the three clusters that are.

Two of them were real and are fixed here and in the previous commit: the
right child's `depth + 1` in the depth-first walk, and aksl_tree_remove
on an empty tree, which without its guard dereferences NULL. Neither had
a test; both do now. That is what the harness is for.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

2026-07-31 08:15:08 -04:00

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