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Fix flaky round_value property test #510

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Merged
gcomte merged 1 commit into from
Mar 30, 2026
Merged

Fix flaky round_value property test #510

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13 changes: 7 additions & 6 deletions src/currency/btc.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -89,17 +89,18 @@ mod tests {
}

#[test]
fn round_value_has_correct_decimal_places(
fn round_value_error_within_half_unit(
amount in 0.0_f64..1.0e8,
unit in arb_btc_unit(),
) {
let rounded = unit.round_value(amount);
let factor = 10_f64.powi(unit.decimal_places().into());
let check = (rounded * factor).round() / factor;
let diff = (rounded - check).abs();
let half_unit = 0.5 / 10_f64.powi(unit.decimal_places().into());
// Allow a small extra tolerance for f64 representation at large magnitudes
let tolerance = half_unit + amount.abs() * f64::EPSILON;
let error = (rounded - amount).abs();
prop_assert!(
diff < 1.0e-10,
"round_value produced too many decimal places: {rounded} (expected {check})"
error <= tolerance,
"round_value({amount}) = {rounded}, error {error} exceeds half unit {half_unit}"
);
}
}
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