money: pessimistic/realistic/optimistic scenarios on the wealth chart (realistic by default), editable assumptions, yearly table and milestones

src/lib/money-tracker/scenarios.test.ts

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+import { describe, expect, it } from 'vitest';
+import { defaultScenarios, runScenario, scenarioInputs, type ScenarioParams } from './scenarios';
+
+const accounts = [
+	{ id: 1, name: 'Revolut', kind: 'checking' },
+	{ id: 4, name: 'Joint', kind: 'checking' },
+	{ id: 5, name: 'Broker', kind: 'investment' },
+	{ id: 9, name: 'Savings', kind: 'savings', includeInTotal: false }
+];
+const inputs = scenarioInputs({
+	accounts,
+	balances: new Map([
+		[1, 200000],
+		[4, 100000],
+		[5, 50000],
+		[9, 999999]
+	]),
+	recurring: [
+		{ name: 'Cargill salary', amountCents: 300000, cadence: 'monthly', accountId: 1 },
+		{ name: 'Gym', amountCents: -3000, cadence: 'monthly', accountId: 1 },
+		{ name: 'Benefit', amountCents: 10000, cadence: 'monthly', accountId: 1, endsOn: '2026-12-31' },
+		{
+			name: 'Rent + utilities (estimate)',
+			amountCents: -180000,
+			cadence: 'monthly',
+			accountId: 4,
+			startsOn: '2027-03-01'
+		},
+		{ name: 'Partner income', amountCents: 250000, cadence: 'monthly', accountId: 4 },
+		{ name: 'Hidden', amountCents: -5000, cadence: 'monthly', accountId: 9 }
+	],
+	forecasts: [
+		{ date: '2026-11-15', amountCents: 28000, description: 'Side job', accountId: 1 },
+		{ date: '2027-09-30', amountCents: 250000, description: 'Bonus Cargill', accountId: 1 }
+	],
+	futureTransactions: [],
+	today: '2026-10-24',
+	endDate: '2030-12-31'
+});
+
+describe('scenarioInputs', () => {
+	it('splits tracker data into balances, salary, personal and household items', () => {
+		expect(inputs.spendableCents).toBe(300000);
+		expect(inputs.investedCents).toBe(50000);
+		expect(inputs.netSalaryCents).toBe(300000);
+		expect(inputs.personal.map((item) => item.name)).toEqual(['Gym', 'Benefit']);
+		expect(inputs.household.map((item) => item.name)).toEqual(['Rent + utilities (estimate)']);
+		expect(inputs.moveDate).toBe('2027-03-01');
+		// Salary extras are modelled by the scenarios, other one-offs pass through.
+		expect(inputs.oneOffs.map((item) => item.description)).toEqual(['Side job']);
+	});
+});
+
+describe('runScenario', () => {
+	const flat: ScenarioParams = {
+		...defaultScenarios.realistic,
+		returnPercent: 0,
+		recoveryPercent: 0,
+		cashRatePercent: 0,
+		sideStartEuros: 0,
+		sideEndEuros: 0,
+		spendGrowthPercent: 0,
+		otherSpendEuros: 0,
+		householdExtraEuros: 0,
+		healthInsuranceEuros: 0,
+		moveCostEuros: 0,
+		bonusPercentOfTarget: 0
+	};
+	it('runs monthly to the end date and starts from today', () => {
+		const result = runScenario(inputs, flat);
+		expect(result.points[0]).toMatchObject({ date: '2026-10-24', total: 350000 });
+		expect(result.end.date).toBe('2030-12-31');
+		expect(result.points).toHaveLength(51);
+		expect(result.years.map((row) => row.year)).toEqual([2026, 2027, 2028, 2029, 2030]);
+	});
+	it('fills the buffer before investing and counts recurring income and costs', () => {
+		const result = runScenario(inputs, flat);
+		const november = result.points[1];
+		expect(november.cash).toBe(500000);
+		// 300k salary + 10k benefit + 28k one-off − 3k gym − 90k pre-move household.
+		expect(november.total).toBeCloseTo(350000 + 300000 + 10000 + 28000 - 3000 - 90000, 0);
+	});
+	it('orders the default scenarios from pessimistic to optimistic', () => {
+		const [pessimistic, realistic, optimistic] = (
+			['pessimistic', 'realistic', 'optimistic'] as const
+		).map((id) => runScenario(inputs, defaultScenarios[id]).end.total);
+		expect(pessimistic).toBeLessThan(realistic);
+		expect(realistic).toBeLessThan(optimistic);
+	});
+	it('applies a crash in its year and a job gap after the contract', () => {
+		const calm = runScenario(inputs, { ...flat, returnPercent: 5, recoveryPercent: 5 });
+		const crash = runScenario(inputs, {
+			...flat,
+			returnPercent: 5,
+			recoveryPercent: 5,
+			crashPercent: -30,
+			crashYear: 2027
+		});
+		expect(crash.end.total).toBeLessThan(calm.end.total);
+		const gap = runScenario(inputs, { ...flat, gapMonths: 3, gapNetEuros: 1000 });
+		expect(gap.end.total).toBeLessThan(runScenario(inputs, flat).end.total);
+	});
+});