1 files changed, 46 insertions, 0 deletions

diff --git a/src/lib/shared/routine-metrics.test.ts b/src/lib/shared/routine-metrics.test.ts
index 4a84eda..a63069c 100644
--- a/src/lib/shared/routine-metrics.test.ts
+++ b/src/lib/shared/routine-metrics.test.ts
@@ -2,6 +2,7 @@ import { describe, it, expect } from 'vitest';
 import {
 	computeRoutineState,
 	computeHealthScore,
+	computeHealthSeries,
 	parseIntervalToDays,
 } from './routine-metrics';
 
@@ -64,6 +65,51 @@ describe('computeRoutineState', () => {
 	});
 });
 
+describe('computeHealthSeries', () => {
+	it('decays from 100 at creation to 0 two periods late when never done', () => {
+		const now = Date.parse(CREATED) + 15 * DAY_MS;
+		const series = computeHealthSeries(routine, [], now);
+		expect(series[0].health).toBe(100);
+		const at8d = series.find((p) => p.at === Date.parse(CREATED) + 8 * DAY_MS);
+		expect(at8d?.health).toBe(86); // 1/7 of a period overdue
+		const last = series[series.length - 1];
+		expect(last.at).toBe(now);
+		expect(last.health).toBe(0); // more than a full period overdue
+	});
+
+	it('resets to 100 right after a completion, then decays again (sawtooth)', () => {
+		const doneAt = Date.parse(CREATED) + 5 * DAY_MS;
+		const now = doneAt + 13 * DAY_MS; // 13 days after the completion
+		const series = computeHealthSeries(
+			routine,
+			[{ routineId: 1, doneAt: new Date(doneAt).toISOString() }],
+			now,
+		);
+		const rightAfter = series.find((p) => p.at >= doneAt);
+		expect(rightAfter?.health).toBe(100);
+		// 8 days after the completion: 1 day into the 7-day period overdue.
+		const at8d = series.find((p) => p.at === doneAt + 8 * DAY_MS);
+		expect(at8d?.health).toBe(86);
+	});
+
+	it('a second completion resets the decay again', () => {
+		const first = Date.parse(CREATED) + 3 * DAY_MS;
+		const second = Date.parse(CREATED) + 10 * DAY_MS;
+		const now = Date.parse(CREATED) + 11 * DAY_MS;
+		const series = computeHealthSeries(
+			routine,
+			[
+				{ routineId: 1, doneAt: new Date(first).toISOString() },
+				{ routineId: 1, doneAt: new Date(second).toISOString() },
+			],
+			now,
+		);
+		// Just after the second completion the routine is back at full health.
+		const nearEnd = series[series.length - 1];
+		expect(nearEnd.health).toBe(100);
+	});
+});
+
 describe('parseIntervalToDays', () => {
 	it('converts units to days', () => {
 		expect(parseIntervalToDays('1d')).toBe(1);