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fix(cargo-coverage-gate): eliminate unkillable format_delta mutant #197

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Merged
martin-kolinek merged 1 commit into from
Sep 23, 2026
Merged

fix(cargo-coverage-gate): eliminate unkillable format_delta mutant #197

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17 changes: 12 additions & 5 deletions crates/cargo-coverage-gate/src/render/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -82,14 +82,21 @@ fn format_delta(outcome: &PackageOutcome) -> String {
return "-<0.1pp".to_owned();
}

// Ordinary values use the displayed precision of one decimal place.
// Ordinary values use the displayed precision of one decimal place. Once
// `delta` clears the sub-precision guard above, its rounded tenth can
// never land back on zero (rounding a value whose magnitude is already
// >= `DELTA_DISPLAY_PRECISION - DELTA_BOUNDARY_TOLERANCE` cannot produce
// `0.0`), so a `rounded < 0.0` branch here is unreachable and would be an
// equivalent mutant against `rounded <= 0.0`. Checking `is_sign_positive`
// after handling zero explicitly avoids that redundant comparison.
let rounded = (delta * 10.0).round() / 10.0;
if rounded > 0.0 {
if rounded == 0.0 {
return "0.0pp".to_owned();
}
if rounded.is_sign_positive() {
format!("+{rounded:.1}pp")
} else if rounded < 0.0 {
format!("{rounded:.1}pp")
} else {
"0.0pp".to_owned()
format!("{rounded:.1}pp")
}
}

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