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P3: depreciation straight-line by days through the final month, schedules by day (defects 22, 9, D-37)

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The final month takes what the months before leave, spread over its days;
a disposed asset stops on its disposal day. A skipped month is caught up
in the month the run is made; a reversed run un-posts its month. New
schedules spread by day; equal-months schedules must start on the 1st.
Amounts round to the currency's own minor unit. Kani and Lean proofs; an
exhaustive search over runs, reversals and disposals.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01T3gXMVt7XJPi6ens1or9Dj
This commit is contained in:
swaitsandClaude Opus 5.5 committed 2026-10-21 14:04:11 -06:00
1 parent 1304b9c0ad
commit b0a9fd8ad4
69 files changed
+10529 -841
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crates/ledger-core/tests/assets.rs
+13 -9
View File
@@ -70,7 +70,7 @@ fn schedule_sums_exactly_to_depreciable_amount() {
// Odd numbers chosen to not divide evenly: 100000 / 60.
let id = van_asset(&mut ledger, 100_000, cost, accum, expense);
let asset = ledger.get_asset(id).unwrap();
let sched = depreciation_schedule(asset, date(2031, 12, 31));
let sched = depreciation_schedule(asset, date(2031, 12, 31)).unwrap();
// 61 calendar months touched (partial first and last), 60 months' worth.
assert_eq!(sched.len(), 61);
let total: Decimal = sched.iter().map(|l| l.amount).sum();
@@ -94,7 +94,7 @@ fn partial_months_complement_to_whole() {
let (mut ledger, cost, accum, expense) = test_ledger();
let id = van_asset(&mut ledger, 100_000, cost, accum, expense);
let asset = ledger.get_asset(id).unwrap();
let sched = depreciation_schedule(asset, date(2031, 12, 31));
let sched = depreciation_schedule(asset, date(2031, 12, 31)).unwrap();
// Jan 2026 (17/31) + Jan 2031 (14/31) = exactly one month's charge.
let monthly = Decimal::from(100_000) / Decimal::from(60);
let monthly_rounded =
@@ -122,7 +122,7 @@ fn salvage_value_is_never_depreciated() {
})
.unwrap();
let asset = ledger.get_asset(id).unwrap();
let sched = depreciation_schedule(asset, date(2030, 12, 31));
let sched = depreciation_schedule(asset, date(2030, 12, 31)).unwrap();
let total: Decimal = sched.iter().map(|l| l.amount).sum();
assert_eq!(total, Decimal::from(45_000));
assert_eq!(sched.last().unwrap().book_value, Decimal::from(5_000));
@@ -133,11 +133,11 @@ fn book_value_tracks_accumulated() {
let (mut ledger, cost, accum, expense) = test_ledger();
let id = van_asset(&mut ledger, 60_000, cost, accum, expense);
let asset = ledger.get_asset(id).unwrap();
let acc = accumulated_depreciation(asset, date(2026, 12, 31));
let acc = accumulated_depreciation(asset, date(2026, 12, 31)).unwrap();
// Jan 2026 prorated 17/31 of 1000 = 548.39, then 11 full months of 1000.
assert_eq!(acc, Decimal::new(54839, 2) + Decimal::from(11_000));
assert_eq!(
book_value(asset, date(2026, 12, 31)),
book_value(asset, date(2026, 12, 31)).unwrap(),
Decimal::from(60_000) - acc
);
}
@@ -281,9 +281,13 @@ fn schedule_through_purchase_date_covers_one_day() {
.unwrap();
let asset = ledger.get_asset(id).unwrap();
// Through the day before purchase: nothing.
assert!(depreciation_schedule(asset, date(2026, 1, 14)).is_empty());
assert!(
depreciation_schedule(asset, date(2026, 1, 14))
.unwrap()
.is_empty()
);
// Through the purchase date itself: one day of the first month.
let one_day = depreciation_schedule(asset, date(2026, 1, 15));
let one_day = depreciation_schedule(asset, date(2026, 1, 15)).unwrap();
assert_eq!(one_day.len(), 1);
assert_eq!(one_day[0].period, "2026-01");
// 62000/62 = 1000/month; 1/31 of that = 32.26.
@@ -302,7 +306,7 @@ fn van_schedule_is_the_hand_computed_one() {
let (mut ledger, cost, accum, expense) = test_ledger();
let id = van_asset(&mut ledger, 60_000, cost, accum, expense);
let asset = ledger.get_asset(id).unwrap();
let sched = depreciation_schedule(asset, date(2032, 1, 1));
let sched = depreciation_schedule(asset, date(2032, 1, 1)).unwrap();
assert_eq!(sched.len(), 61);
let mut accumulated = Decimal::ZERO;
for (k, line) in sched.iter().enumerate() {
@@ -421,7 +425,7 @@ fn one_month_useful_life_is_valid() {
})
.unwrap();
let asset = ledger.get_asset(id).unwrap();
let sched = depreciation_schedule(asset, date(2026, 12, 31));
let sched = depreciation_schedule(asset, date(2026, 12, 31)).unwrap();
// A one-month life starting Mar 10 spans two calendar months.
assert_eq!(sched.len(), 2);
// March: 22/31 of 300 = 212.90.