Closes boxed#196. A ternary is a branch that nothing here mutated. Branch coverage does not see an uncovered arm either, so an untested arm read as a pass twice over. `grep -rn "IfExp\|ternary\|if_exp"` over src/, tests/ and docs/ returned nothing before this. `operator_if_exp` yields two mutants per ternary, neutralising the condition in each direction: a if b else c -> a if (b) and False else c a if (b) or True else c On the parentheses, which boxed#478's review asked to drop: they are load-bearing for the `and False` half. `and` binds tighter than a top-level `or`, so an unparenthesised `b or c` becomes `b or (c and False)`, which still takes the true branch whenever `b` is truthy. Over the 16 assignments of a `a if b or c else d`: (b or c) and False differs from the original on 6 of 16 b or c and False differs on 2 of 16, and only when b is falsy `or True` genuinely does not need them — parenthesised and not are identical on all 16 — but wrapping both keeps one rule rather than two, and costs nothing. test_function_with_annotation shifts because its fixture contains a ternary: the two new mutants take numbers 1 and 2 and push the arithmetic and index mutants to 3-5. The three original assertions are kept, renumbered, and the two new mutants are asserted alongside them, so the test still shows nothing was lost. Measured on 4f12080, `pytest tests/`: 12 failed / 345 passed before and after, with an identical FAILED set. (tests/utils/test_safe_setproctitle.py is flaky here regardless of this change — 1 pass in 5 runs both with and without it.) ruff check, ruff format --check and mypy pass. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Commits

Commits on Aug 2, 2026

feat: mutate ternary conditions