Files
accounted/lib/salary/__tests__/calculation-engine.test.ts
T
Jakob WennbergandClaude Sonnet 5 ec27228a8e style: remove em/en dashes repo-wide, add CLAUDE.md rule against them (#890)
Em dashes (—) and en dashes (–) had spread across comments, docs, tests,
and a few UI strings, reading as AI-generated boilerplate rather than
house style. Replaced each with punctuation matching its context: colon
for explanatory clauses, comma for asides, plain hyphen for numeric/legal
ranges (e.g. "21-23§"), "to"/"till" for date ranges, parentheses for
paired-dash asides. messages/en.json and messages/sv.json were fixed by
hand together to keep sv/en in sync.

Left untouched where the dash is the functional subject rather than
decorative punctuation: date-range-parser.ts's separator regex,
charset-repair.ts's CP1252 byte-mapping table (and its test), the SIE
encoding mojibake docs, generic-csv.ts's minus-sign normalizer, the
agent system-prompt files that already instruct against em dashes, and
a golden iXBRL test fixture compared byte-for-byte.

Also fixes two bugs surfaced along the way: an off-by-one in
ApiKeysPanel's scope-label split (a leftover from an earlier partial
pass), and a charset-repair test that had lost the literal en-dash it
exists to verify.

Regenerated the agent atom seed migration (skills:generate) since 27
SKILL.md files changed. Added a CLAUDE.md rule against em/en dashes,
with an explicit carve-out for the functional-dash cases above.

Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>
2026-07-04 15:58:06 +02:00

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import { describe, it, expect, vi, beforeEach } from 'vitest'
import {
calculateSalary,
calculateKarensavdrag,
calculateSjuklon,
calculateAvgifterRate,
calculateVacationAccrual,
prorateBaseSalaryForPeriod,
} from '../calculation-engine'
import type { PayrollConfig } from '../payroll-config'
import type { TaxTableRate } from '../tax-tables'
// Mock personnummer module
vi.mock('../personnummer', () => ({
decryptPersonnummer: (encrypted: string) => {
// Return mock personnummer based on encrypted value
if (encrypted === 'mock_old_person') return '193501011234'
if (encrypted === 'mock_young_person') return '200301011234'
if (encrypted === 'mock_senior_person') return '195801011234'
// Generic helper: 'mock_born_YYYY' resolves to a Jan-1 birth in YYYY.
// Used by ungdomsrabatt boundary tests so each case names its own year
// explicitly rather than depending on a global mock alias.
const m = /^mock_born_(\d{4})$/.exec(encrypted)
if (m) return `${m[1]}01011234`
return '199001011234' // Default: born 1990
},
calculateAgeAtYearStart: (pnr: string, year: number) => {
const birthYear = parseInt(pnr.slice(0, 4))
return year - birthYear
},
}))
const config2026: PayrollConfig = {
configYear: 2026,
avgifterTotal: 0.3142,
avgifterAlderspension: 0.1021,
avgifterSjukforsakring: 0.0355,
avgifterForaldraforsakring: 0.0200,
avgifterEfterlevandepension: 0.0030,
avgifterArbetsmarknad: 0.0264,
avgifterArbetsskada: 0.0010,
avgifterAllmanLoneavgift: 0.1262,
avgifterReduced65plus: 0.1021,
avgifterYouthRate: 0.2081,
avgifterYouthSalaryCap: 25000,
avgifterVaxaStodRate: 0.1021,
avgifterVaxaStodCap: 35000,
avgifterMinimumAnnual: 1000,
egenavgifterTotal: 0.2897,
slpRate: 0.2426,
prisbasbelopp: 59200,
inkomstbasbelopp: 83400,
maxPgi: 625500,
sgiCeiling: 592000,
statligSkattBrytpunkt: 660400,
traktamenteHeldag: 300,
traktamenteHalvdag: 150,
traktamenteNatt: 150,
milersattningEgenBil: 25,
milersattningFormansbilFossil: 12,
milersattningFormansbilEl: 9.50,
kostformanHeldag: 310,
kostformanLunch: 124,
kostformanFrukost: 62,
friskvardCap: 5000,
bilformanSlr: 0.0255,
sjuklonRate: 0.80,
karensavdragFactor: 0.20,
maxKarensavdragPerYear: 10,
reducedAvgiftAge: 67,
}
const emptyTaxRates: TaxTableRate[] = []
function makeBasicInput(overrides = {}) {
return {
employmentType: 'employee' as const,
salaryType: 'monthly' as const,
monthlySalary: 40000,
employmentDegree: 100,
taxTableNumber: null,
taxColumn: 1,
isSidoinkomst: false,
jamkningPercentage: null,
jamkningValidFrom: null,
jamkningValidTo: null,
fSkattStatus: 'a_skatt',
personnummer: 'mock_standard',
paymentDate: '2026-04-25',
vacationRule: 'procentregeln' as const,
vacationDaysPerYear: 25,
semestertillaggRate: 0.0043,
vaxaStodEligible: false,
vaxaStodStart: null,
vaxaStodEnd: null,
lineItems: [],
...overrides,
}
}
describe('calculateSalary', () => {
it('calculates basic monthly salary correctly', () => {
const result = calculateSalary(makeBasicInput(), config2026, emptyTaxRates)
expect(result.grossSalary).toBe(40000)
// With no tax table, falls back to 30%
expect(result.taxWithheld).toBe(12000)
expect(result.netSalary).toBe(28000)
expect(result.avgifterRate).toBe(0.3142)
expect(result.avgifterAmount).toBe(Math.round(40000 * 0.3142 * 100) / 100)
expect(result.vacationAccrual).toBe(Math.round(40000 * 0.12 * 100) / 100)
expect(result.steps.length).toBeGreaterThan(0)
})
it('applies employment degree', () => {
const result = calculateSalary(
makeBasicInput({ employmentDegree: 50 }),
config2026,
emptyTaxRates
)
expect(result.grossSalary).toBe(20000)
expect(result.taxWithheld).toBe(6000) // 30% of 20000
expect(result.netSalary).toBe(14000)
})
it('calculates hourly salary', () => {
const result = calculateSalary(
makeBasicInput({
salaryType: 'hourly',
monthlySalary: 0,
hourlyRate: 250,
hoursWorked: 160,
}),
config2026,
emptyTaxRates
)
expect(result.grossSalary).toBe(40000) // 250 * 160
})
it('applies sidoinkomst flat 30%', () => {
const result = calculateSalary(
makeBasicInput({ isSidoinkomst: true }),
config2026,
emptyTaxRates
)
expect(result.taxWithheld).toBe(12000) // 30% of 40000
})
it('applies f-skatt with 0% withholding', () => {
const result = calculateSalary(
makeBasicInput({ fSkattStatus: 'f_skatt' }),
config2026,
emptyTaxRates
)
expect(result.taxWithheld).toBe(0)
expect(result.netSalary).toBe(40000)
})
it('applies unverified flat 30%', () => {
const result = calculateSalary(
makeBasicInput({ fSkattStatus: 'not_verified' }),
config2026,
emptyTaxRates
)
expect(result.taxWithheld).toBe(12000)
})
it('applies jämkning when valid', () => {
const result = calculateSalary(
makeBasicInput({
jamkningPercentage: 15,
jamkningValidFrom: '2026-01-01',
jamkningValidTo: '2026-12-31',
}),
config2026,
emptyTaxRates
)
expect(result.taxWithheld).toBe(6000) // 15% of 40000
})
it('does not apply jämkning when outside date range', () => {
const result = calculateSalary(
makeBasicInput({
jamkningPercentage: 15,
jamkningValidFrom: '2025-01-01',
jamkningValidTo: '2025-12-31',
paymentDate: '2026-04-25',
}),
config2026,
emptyTaxRates
)
// Should fall back to 30% since jämkning expired
expect(result.taxWithheld).toBe(12000)
})
it('handles line item additions', () => {
const result = calculateSalary(
makeBasicInput({
lineItems: [
{ itemType: 'bonus', amount: 5000, isTaxable: true, isAvgiftBasis: true, isVacationBasis: true, isGrossDeduction: false, isNetDeduction: false },
],
}),
config2026,
emptyTaxRates
)
expect(result.grossSalary).toBe(45000) // 40000 + 5000
expect(result.taxWithheld).toBe(13500) // 30% of 45000
})
it('applies gross deductions before tax', () => {
const result = calculateSalary(
makeBasicInput({
lineItems: [
{ itemType: 'gross_deduction_pension', amount: -5000, isTaxable: true, isAvgiftBasis: true, isVacationBasis: false, isGrossDeduction: true, isNetDeduction: false },
],
}),
config2026,
emptyTaxRates
)
expect(result.grossSalary).toBe(35000) // 40000 - 5000
expect(result.grossDeductions).toBe(5000)
expect(result.taxWithheld).toBe(10500) // 30% of 35000 (tax on reduced amount)
})
it('applies net deductions after tax', () => {
const result = calculateSalary(
makeBasicInput({
lineItems: [
{ itemType: 'net_deduction_advance', amount: -3000, isTaxable: false, isAvgiftBasis: false, isVacationBasis: false, isGrossDeduction: false, isNetDeduction: true },
],
}),
config2026,
emptyTaxRates
)
expect(result.grossSalary).toBe(40000) // Unaffected
expect(result.taxWithheld).toBe(12000) // 30% of 40000 (tax on full amount)
expect(result.netDeductions).toBe(3000)
expect(result.netSalary).toBe(25000) // 40000 - 12000 - 3000
})
it('calculates vacation accrual with procentregeln', () => {
const result = calculateSalary(
makeBasicInput({ vacationRule: 'procentregeln', vacationDaysPerYear: 25 }),
config2026,
emptyTaxRates
)
expect(result.vacationAccrual).toBe(Math.round(40000 * 0.12 * 100) / 100)
})
it('uses 14.4% for 30+ vacation days', () => {
const result = calculateSalary(
makeBasicInput({ vacationRule: 'procentregeln', vacationDaysPerYear: 30 }),
config2026,
emptyTaxRates
)
expect(result.vacationAccrual).toBe(Math.round(40000 * 0.144 * 100) / 100)
})
it('pays semesterersättning directly when vacation_rule = semesterersattning', () => {
const result = calculateSalary(
makeBasicInput({ vacationRule: 'semesterersattning', vacationDaysPerYear: 25 }),
config2026,
emptyTaxRates
)
const expectedCompensation = Math.round(40000 * 0.12 * 100) / 100
expect(result.vacationCompensation).toBe(expectedCompensation)
expect(result.grossSalary).toBe(40000 + expectedCompensation)
expect(result.vacationAccrual).toBe(0)
expect(result.vacationAccrualAvgifter).toBe(0)
// Avgifter basis includes the compensation
expect(result.avgifterBasis).toBe(40000 + expectedCompensation)
})
it('uses 14.4% for semesterersättning with 30+ vacation days', () => {
const result = calculateSalary(
makeBasicInput({ vacationRule: 'semesterersattning', vacationDaysPerYear: 30 }),
config2026,
emptyTaxRates
)
expect(result.vacationCompensation).toBe(Math.round(40000 * 0.144 * 100) / 100)
expect(result.vacationAccrual).toBe(0)
})
it('semesterersättning includes vacation-basis line items (e.g. overtime)', () => {
const result = calculateSalary(
makeBasicInput({
vacationRule: 'semesterersattning',
vacationDaysPerYear: 25,
lineItems: [
{ itemType: 'overtime', amount: 5000, isTaxable: true, isAvgiftBasis: true, isVacationBasis: true, isGrossDeduction: false, isNetDeduction: false },
],
}),
config2026,
emptyTaxRates
)
// 12% × (40000 base + 5000 overtime) = 5400
expect(result.vacationCompensation).toBe(5400)
// 40000 base + 5000 overtime + 5400 semesterersättning
expect(result.grossSalary).toBe(50400)
})
it('does not double-count base salary line items in vacation basis', () => {
// The API auto-creates a monthly_salary line item with amount = baseSalary
// and is_vacation_basis: true. The engine must not add it on top of its
// own baseSalary computation: otherwise procentregeln/semesterersättning
// would compute 2× the correct amount.
const monthlyResult = calculateSalary(
makeBasicInput({
monthlySalary: 40000,
employmentDegree: 50, // grundlön = 20000
vacationRule: 'procentregeln',
lineItems: [
{ itemType: 'monthly_salary', amount: 20000, isTaxable: true, isAvgiftBasis: true, isVacationBasis: true, isGrossDeduction: false, isNetDeduction: false },
],
}),
config2026,
emptyTaxRates
)
expect(monthlyResult.vacationAccrual).toBe(2400) // 12% × 20000, not 12% × 40000
const compResult = calculateSalary(
makeBasicInput({
monthlySalary: 40000,
employmentDegree: 50,
vacationRule: 'semesterersattning',
lineItems: [
{ itemType: 'monthly_salary', amount: 20000, isTaxable: true, isAvgiftBasis: true, isVacationBasis: true, isGrossDeduction: false, isNetDeduction: false },
],
}),
config2026,
emptyTaxRates
)
expect(compResult.vacationCompensation).toBe(2400)
expect(compResult.grossSalary).toBe(22400) // 20000 base + 2400 comp
})
it('skips accrual when vacation_rule = none', () => {
const result = calculateSalary(
makeBasicInput({ vacationRule: 'none' }),
config2026,
emptyTaxRates
)
expect(result.vacationAccrual).toBe(0)
expect(result.vacationCompensation).toBe(0)
expect(result.grossSalary).toBe(40000)
})
it('adds benefit values to tax base but not gross', () => {
const result = calculateSalary(
makeBasicInput({
lineItems: [
{ itemType: 'benefit_car', amount: 3000, isTaxable: true, isAvgiftBasis: true, isVacationBasis: false, isGrossDeduction: false, isNetDeduction: false },
],
}),
config2026,
emptyTaxRates
)
expect(result.grossSalary).toBe(40000) // Benefits don't add to gross
expect(result.benefitValues).toBe(3000)
expect(result.taxableIncome).toBe(43000) // gross + benefits
expect(result.taxWithheld).toBe(12900) // 30% of 43000
expect(result.netSalary).toBe(27100) // 40000 - 12900
})
it('includes employer cost calculation', () => {
const result = calculateSalary(makeBasicInput(), config2026, emptyTaxRates)
const expectedAvgifter = Math.round(40000 * 0.3142 * 100) / 100
const expectedVacation = Math.round(40000 * 0.12 * 100) / 100
const expectedVacationAvgifter = Math.round(expectedVacation * 0.3142 * 100) / 100
const expectedCost = Math.round((40000 + expectedAvgifter + expectedVacation + expectedVacationAvgifter) * 100) / 100
expect(result.totalEmployerCost).toBe(expectedCost)
})
})
// ============================================================
// Partial-month employment proration
// ============================================================
//
// May 2026 calendar (Mon-Fri only):
// May 1 (Fri), May 4-8 (5), May 11-15 (5), May 18-22 (5), May 25-29 (5)
// → 21 workdays total in May.
// An employee hired May 15 (Fri) works May 15, 18-22, 25-29 → 11 workdays.
// 11 / 21 ≈ 0.5238 → 40 000 SEK × 0.5238 ≈ 20 952,38 SEK.
describe('partial-month employment proration', () => {
it('prorates base salary for an employee hired mid-month', () => {
const result = calculateSalary(
makeBasicInput({
periodStart: '2026-05-01',
periodEnd: '2026-05-31',
employmentStart: '2026-05-15',
employmentEnd: null,
}),
config2026,
emptyTaxRates,
)
// 40 000 × 11 / 21 = 20 952,38 (rounded via engine's r())
expect(result.grossSalary).toBeCloseTo(20952.38, 2)
})
it('prorates base salary for an employee terminated mid-month', () => {
const result = calculateSalary(
makeBasicInput({
periodStart: '2026-05-01',
periodEnd: '2026-05-31',
employmentStart: '2020-01-01',
employmentEnd: '2026-05-15',
}),
config2026,
emptyTaxRates,
)
// May 1, 4-8, 11-15 = 11 workdays → 40 000 × 11 / 21
expect(result.grossSalary).toBeCloseTo(20952.38, 2)
})
it('does not prorate when the employee covers the full period', () => {
const result = calculateSalary(
makeBasicInput({
periodStart: '2026-05-01',
periodEnd: '2026-05-31',
employmentStart: '2024-01-01',
employmentEnd: null,
}),
config2026,
emptyTaxRates,
)
expect(result.grossSalary).toBe(40000)
})
it('returns 0 gross when employment does not overlap the period', () => {
const result = calculateSalary(
makeBasicInput({
periodStart: '2026-05-01',
periodEnd: '2026-05-31',
employmentStart: '2026-06-01',
employmentEnd: null,
}),
config2026,
emptyTaxRates,
)
expect(result.grossSalary).toBe(0)
})
it('combines employment proration with employment_degree', () => {
const result = calculateSalary(
makeBasicInput({
employmentDegree: 50,
periodStart: '2026-05-01',
periodEnd: '2026-05-31',
employmentStart: '2026-05-15',
employmentEnd: null,
}),
config2026,
emptyTaxRates,
)
// 40 000 × 50% × 11 / 21 = 20 000 × 11 / 21 ≈ 10 476,19
expect(result.grossSalary).toBeCloseTo(10476.19, 2)
})
it('skips proration when period bounds are missing (backward compat)', () => {
const result = calculateSalary(
makeBasicInput({
employmentStart: '2026-05-15',
employmentEnd: null,
}),
config2026,
emptyTaxRates,
)
expect(result.grossSalary).toBe(40000)
})
it('subtracts unpaid_leave once on top of proration (no double-counting)', () => {
// 40 000 × 11/21 (mid-month hire) − 2 × 40 000/21 (two unpaid days)
// = 20 952,38 − 3 809,52
// = 17 142,86
const result = calculateSalary(
makeBasicInput({
periodStart: '2026-05-01',
periodEnd: '2026-05-31',
employmentStart: '2026-05-15',
employmentEnd: null,
lineItems: [
{
itemType: 'unpaid_leave',
amount: -3809.52, // = 2 × Math.round((40000/21) * 100) / 100
isTaxable: true,
isAvgiftBasis: true,
isVacationBasis: false,
isGrossDeduction: false,
isNetDeduction: false,
},
],
}),
config2026,
emptyTaxRates,
)
expect(result.grossSalary).toBeCloseTo(17142.86, 2)
})
})
describe('prorateBaseSalaryForPeriod', () => {
it('returns 1 when all dates are missing', () => {
expect(prorateBaseSalaryForPeriod(undefined, undefined, undefined, undefined)).toBe(1)
})
it('returns 1 when employment fully covers the period', () => {
expect(
prorateBaseSalaryForPeriod('2020-01-01', null, '2026-05-01', '2026-05-31'),
).toBe(1)
})
it('returns 11/21 for May 2026 mid-month hire on the 15th', () => {
const ratio = prorateBaseSalaryForPeriod(
'2026-05-15',
null,
'2026-05-01',
'2026-05-31',
)
expect(ratio).toBeCloseTo(11 / 21, 6)
})
it('returns 0 when employment ends before the period starts', () => {
expect(
prorateBaseSalaryForPeriod('2020-01-01', '2026-04-30', '2026-05-01', '2026-05-31'),
).toBe(0)
})
it('returns 0 when employment starts after the period ends', () => {
expect(
prorateBaseSalaryForPeriod('2026-06-01', null, '2026-05-01', '2026-05-31'),
).toBe(0)
})
})
// ============================================================
// Hardening: realistic API flow & cross-rule invariants
// ============================================================
//
// These tests mirror the actual production input shape, where the
// "Lägg till anställd" endpoint auto-creates a base salary line item
// (monthly_salary or hourly_salary) before the engine runs. The plain
// `makeBasicInput()` cases above don't include that line item, so they
// miss the double-counting class of bug. The helper below adds it.
type LineItem = {
itemType: string
amount: number
isTaxable: boolean
isAvgiftBasis: boolean
isVacationBasis: boolean
isGrossDeduction: boolean
isNetDeduction: boolean
}
function baseLineItem(amount: number, type: 'monthly_salary' | 'hourly_salary' = 'monthly_salary'): LineItem {
return {
itemType: type,
amount,
isTaxable: true,
isAvgiftBasis: true,
isVacationBasis: true,
isGrossDeduction: false,
isNetDeduction: false,
}
}
function lineItem(overrides: Partial<LineItem> & { itemType: string; amount: number }): LineItem {
return {
isTaxable: true,
isAvgiftBasis: true,
isVacationBasis: false,
isGrossDeduction: false,
isNetDeduction: false,
...overrides,
}
}
describe('hardening: vacation rule contract', () => {
// Same input across all 4 vacation rules, locking in the relationships
// between them. This is the contract a Swedish accountant relies on.
const base = {
monthlySalary: 40000,
employmentDegree: 100,
vacationDaysPerYear: 25,
semestertillaggRate: 0.0043,
lineItems: [baseLineItem(40000)],
}
it('procentregeln: 12% accrued, 0 paid out', () => {
const r = calculateSalary(
makeBasicInput({ ...base, vacationRule: 'procentregeln' }),
config2026, emptyTaxRates
)
expect(r.grossSalary).toBe(40000)
expect(r.vacationCompensation).toBe(0)
expect(r.vacationAccrual).toBe(4800)
})
it('semesterersattning: 0 accrued, 12% paid out into gross', () => {
const r = calculateSalary(
makeBasicInput({ ...base, vacationRule: 'semesterersattning' }),
config2026, emptyTaxRates
)
expect(r.grossSalary).toBe(44800) // 40000 + 4800
expect(r.vacationCompensation).toBe(4800)
expect(r.vacationAccrual).toBe(0)
})
it('sammaloneregeln: only tillägg accrued, 0 paid out', () => {
const r = calculateSalary(
makeBasicInput({ ...base, vacationRule: 'sammaloneregeln' }),
config2026, emptyTaxRates
)
expect(r.grossSalary).toBe(40000)
expect(r.vacationCompensation).toBe(0)
// dagslön 40000/21 × 0.43% × 25 ≈ 204.76
expect(r.vacationAccrual).toBeCloseTo(204.76, 1)
})
it('none: nothing accrued, nothing paid out', () => {
const r = calculateSalary(
makeBasicInput({ ...base, vacationRule: 'none' }),
config2026, emptyTaxRates
)
expect(r.grossSalary).toBe(40000)
expect(r.vacationCompensation).toBe(0)
expect(r.vacationAccrual).toBe(0)
expect(r.vacationAccrualAvgifter).toBe(0)
})
it('procentregeln and semesterersattning produce identical totalEmployerCost', () => {
// Different bookkeeping (2920 accrual vs 7285 cash) but the same total
// cost to the company. Locking this is the cheapest sanity check.
const proc = calculateSalary(
makeBasicInput({ ...base, vacationRule: 'procentregeln' }),
config2026, emptyTaxRates
)
const semer = calculateSalary(
makeBasicInput({ ...base, vacationRule: 'semesterersattning' }),
config2026, emptyTaxRates
)
expect(semer.totalEmployerCost).toBeCloseTo(proc.totalEmployerCost, 1)
})
})
describe('hardening: boundaries', () => {
it('vacation_days_per_year = 29 uses 12%', () => {
const r = calculateSalary(
makeBasicInput({ vacationRule: 'procentregeln', vacationDaysPerYear: 29 }),
config2026, emptyTaxRates
)
expect(r.vacationAccrual).toBeCloseTo(40000 * 0.12, 1)
})
it('vacation_days_per_year = 30 uses 14.4%', () => {
const r = calculateSalary(
makeBasicInput({ vacationRule: 'procentregeln', vacationDaysPerYear: 30 }),
config2026, emptyTaxRates
)
expect(r.vacationAccrual).toBeCloseTo(40000 * 0.144, 1)
})
it('semesterersättning at 29 vs 30 days flips rate', () => {
const r29 = calculateSalary(
makeBasicInput({ vacationRule: 'semesterersattning', vacationDaysPerYear: 29 }),
config2026, emptyTaxRates
)
const r30 = calculateSalary(
makeBasicInput({ vacationRule: 'semesterersattning', vacationDaysPerYear: 30 }),
config2026, emptyTaxRates
)
expect(r29.vacationCompensation).toBeCloseTo(40000 * 0.12, 1)
expect(r30.vacationCompensation).toBeCloseTo(40000 * 0.144, 1)
})
it('jämkning expires on validTo (inclusive)', () => {
const r = calculateSalary(
makeBasicInput({
jamkningPercentage: 10,
jamkningValidFrom: '2026-01-01',
jamkningValidTo: '2026-04-30',
paymentDate: '2026-04-30',
}),
config2026, emptyTaxRates
)
expect(r.taxWithheld).toBe(4000) // 10% × 40000: still valid on the last day
})
it('jämkning not applied the day after validTo', () => {
const r = calculateSalary(
makeBasicInput({
jamkningPercentage: 10,
jamkningValidFrom: '2026-01-01',
jamkningValidTo: '2026-04-30',
paymentDate: '2026-05-01',
}),
config2026, emptyTaxRates
)
expect(r.taxWithheld).toBe(12000) // fallback 30%
})
})
describe('hardening: sammalöneregeln', () => {
it('part-time worker gets half the tillägg of a full-timer', () => {
const full = calculateSalary(
makeBasicInput({
vacationRule: 'sammaloneregeln', monthlySalary: 40000, employmentDegree: 100,
lineItems: [baseLineItem(40000)],
}),
config2026, emptyTaxRates
)
const half = calculateSalary(
makeBasicInput({
vacationRule: 'sammaloneregeln', monthlySalary: 40000, employmentDegree: 50,
lineItems: [baseLineItem(20000)],
}),
config2026, emptyTaxRates
)
expect(half.vacationAccrual).toBeCloseTo(full.vacationAccrual / 2, 1)
})
it('respects custom semestertillagg_rate (CBA 0.8%)', () => {
const r = calculateSalary(
makeBasicInput({
vacationRule: 'sammaloneregeln', semestertillaggRate: 0.008,
lineItems: [baseLineItem(40000)],
}),
config2026, emptyTaxRates
)
// 40000/21 × 0.8% × 25 ≈ 380.95
expect(r.vacationAccrual).toBeCloseTo(380.95, 1)
})
})
describe('hardening: realistic combined scenarios', () => {
it('monthly worker with overtime, benefit, pension deduction, semesterersättning', () => {
const r = calculateSalary(
makeBasicInput({
vacationRule: 'semesterersattning',
vacationDaysPerYear: 25,
lineItems: [
baseLineItem(40000),
lineItem({ itemType: 'overtime', amount: 5000, isVacationBasis: true }),
lineItem({ itemType: 'benefit_car', amount: 3000 }), // not vacation basis
lineItem({ itemType: 'gross_deduction_pension', amount: -2000, isGrossDeduction: true, isVacationBasis: false }),
],
}),
config2026, emptyTaxRates
)
// Vacation basis = 40000 base + 5000 overtime (benefits excluded, gross deduction excluded)
// Semesterersättning = 12% × 45000 = 5400
expect(r.vacationCompensation).toBe(5400)
// Gross = 40000 + 5000 overtime + 5400 semer − 2000 pension = 48400
expect(r.grossSalary).toBe(48400)
// Tax base = gross + benefits = 48400 + 3000 = 51400
expect(r.taxableIncome).toBe(51400)
expect(r.taxWithheld).toBe(15420) // 30% fallback
// Avgifter basis = gross + benefits = 51400
expect(r.avgifterBasis).toBe(51400)
expect(r.vacationAccrual).toBe(0)
})
it('hourly worker with no manual line items still gets correct semesterersättning', () => {
// Production sends an hourly_salary line item with the computed amount.
const r = calculateSalary(
makeBasicInput({
salaryType: 'hourly',
monthlySalary: 0,
hourlyRate: 250,
hoursWorked: 160,
vacationRule: 'semesterersattning',
lineItems: [baseLineItem(40000, 'hourly_salary')],
}),
config2026, emptyTaxRates
)
expect(r.vacationCompensation).toBe(4800) // 12% × 40000, not 12% × 80000
expect(r.grossSalary).toBe(44800)
})
it('benefits do not inflate semesterersättning basis', () => {
// Förmånsvärden are NOT vacation basis (employee doesn't earn vacation
// pay on the value of their company car). The engine must exclude them.
const r = calculateSalary(
makeBasicInput({
vacationRule: 'semesterersattning',
lineItems: [
baseLineItem(40000),
lineItem({ itemType: 'benefit_car', amount: 10000, isVacationBasis: false }),
],
}),
config2026, emptyTaxRates
)
// Should be 12% × 40000 = 4800, not 12% × 50000 = 6000
expect(r.vacationCompensation).toBe(4800)
})
})
describe('hardening: invariants', () => {
it('netSalary + taxWithheld + netDeductions = grossSalary (always)', () => {
for (const rule of ['procentregeln', 'sammaloneregeln', 'none', 'semesterersattning'] as const) {
const r = calculateSalary(
makeBasicInput({
vacationRule: rule,
lineItems: [
baseLineItem(40000),
lineItem({ itemType: 'net_deduction_advance', amount: -2000, isNetDeduction: true, isTaxable: false, isAvgiftBasis: false }),
],
}),
config2026, emptyTaxRates
)
const reconstructed = Math.round((r.netSalary + r.taxWithheld + r.netDeductions) * 100) / 100
expect(reconstructed).toBeCloseTo(r.grossSalary, 1)
}
})
it('totalEmployerCost = grossSalary + avgifterAmount + vacationAccrual + vacationAccrualAvgifter', () => {
for (const rule of ['procentregeln', 'sammaloneregeln', 'none', 'semesterersattning'] as const) {
const r = calculateSalary(
makeBasicInput({ vacationRule: rule, lineItems: [baseLineItem(40000)] }),
config2026, emptyTaxRates
)
const expected = Math.round((r.grossSalary + r.avgifterAmount + r.vacationAccrual + r.vacationAccrualAvgifter) * 100) / 100
expect(expected).toBeCloseTo(r.totalEmployerCost, 1)
}
})
it('avgifterAmount = avgifterBasis × avgifterRate (within rounding)', () => {
const r = calculateSalary(
makeBasicInput({ lineItems: [baseLineItem(40000)] }),
config2026, emptyTaxRates
)
expect(r.avgifterAmount).toBeCloseTo(r.avgifterBasis * r.avgifterRate, 1)
})
it('semesterersattning never produces both vacationAccrual and vacationCompensation', () => {
const r = calculateSalary(
makeBasicInput({
vacationRule: 'semesterersattning',
lineItems: [baseLineItem(40000)],
}),
config2026, emptyTaxRates
)
expect(r.vacationAccrual).toBe(0)
expect(r.vacationCompensation).toBeGreaterThan(0)
})
})
describe('hardening: tax table lookup (not just flat fallback)', () => {
const taxRates: TaxTableRate[] = [
{ tableYear: 2026, tableNumber: 32, columnNumber: 1, incomeFrom: 0, incomeTo: 20000, taxAmount: 3000 },
{ tableYear: 2026, tableNumber: 32, columnNumber: 1, incomeFrom: 20001, incomeTo: 30000, taxAmount: 5500 },
{ tableYear: 2026, tableNumber: 32, columnNumber: 1, incomeFrom: 30001, incomeTo: 50000, taxAmount: 10000 },
]
it('uses table lookup when taxTableNumber is set', () => {
const r = calculateSalary(
makeBasicInput({ taxTableNumber: 32, taxColumn: 1, monthlySalary: 25000, lineItems: [baseLineItem(25000)] }),
config2026, taxRates
)
expect(r.taxWithheld).toBe(5500)
})
it('semesterersättning pushes brutto into a higher tax bracket', () => {
// Base 25000 + 12% semer = 28000, still in 20001-30000 bracket
const semer = calculateSalary(
makeBasicInput({
taxTableNumber: 32, taxColumn: 1, monthlySalary: 25000,
vacationRule: 'semesterersattning',
lineItems: [baseLineItem(25000)],
}),
config2026, taxRates
)
expect(semer.grossSalary).toBe(28000)
expect(semer.taxWithheld).toBe(5500) // still bracket 2
})
})
describe('calculateVacationAccrual (standalone export)', () => {
it('procentregeln: 12% of vacationBasis under 30 days', () => {
const r = calculateVacationAccrual({
monthlySalary: 40000,
vacationRule: 'procentregeln',
vacationDaysPerYear: 25,
semestertillaggRate: 0.0043,
vacationBasis: 40000,
})
expect(r.accrual).toBe(4800)
})
it('procentregeln: 14.4% at 30+ days', () => {
const r = calculateVacationAccrual({
monthlySalary: 40000,
vacationRule: 'procentregeln',
vacationDaysPerYear: 30,
semestertillaggRate: 0.0043,
vacationBasis: 40000,
})
expect(r.accrual).toBeCloseTo(5760, 1)
})
it('sammaloneregeln: uses vacationBasis, not monthlySalary (degree-adjusted)', () => {
// 50% worker: caller passes vacationBasis = 20000 (degree-adjusted),
// not the raw 40000 monthlySalary. Result must be half the full-time amount.
const partTime = calculateVacationAccrual({
monthlySalary: 40000, // ignored
vacationRule: 'sammaloneregeln',
vacationDaysPerYear: 25,
semestertillaggRate: 0.0043,
vacationBasis: 20000,
})
const fullTime = calculateVacationAccrual({
monthlySalary: 40000,
vacationRule: 'sammaloneregeln',
vacationDaysPerYear: 25,
semestertillaggRate: 0.0043,
vacationBasis: 40000,
})
expect(partTime.accrual).toBeCloseTo(fullTime.accrual / 2, 1)
// Independent check: 20000/21 × 0.43% × 25 ≈ 102.38
expect(partTime.accrual).toBeCloseTo(102.38, 1)
})
it('semesterersattning: 0 accrual with the correct step label', () => {
const r = calculateVacationAccrual({
monthlySalary: 40000,
vacationRule: 'semesterersattning',
vacationDaysPerYear: 25,
semestertillaggRate: 0.0043,
vacationBasis: 40000,
})
expect(r.accrual).toBe(0)
expect(r.steps[0].label).toContain('semesterersättning betald direkt')
})
it('none: 0 accrual, no "betald direkt" wording', () => {
const r = calculateVacationAccrual({
monthlySalary: 40000,
vacationRule: 'none',
vacationDaysPerYear: 25,
semestertillaggRate: 0.0043,
vacationBasis: 40000,
})
expect(r.accrual).toBe(0)
expect(r.steps[0].label).toBe('Semesteravsättning (avstängd)')
expect(r.steps[0].label).not.toContain('semesterersättning')
})
})
describe('calculateKarensavdrag', () => {
it('calculates 20% of weekly sjuklön', () => {
// Formula: 20% × (40000 × 12/52 × 0.80)
const expected = Math.round(0.20 * (40000 * 12 / 52 * 0.80) * 100) / 100
expect(calculateKarensavdrag(40000, config2026)).toBe(expected)
})
})
describe('calculateSjuklon', () => {
it('calculates karensavdrag + sjuklön for sick days', () => {
const result = calculateSjuklon(40000, 5, config2026)
expect(result.karensavdrag).toBeGreaterThan(0)
expect(result.sjuklon).toBeGreaterThan(0)
expect(result.steps.length).toBeGreaterThan(0)
})
it('handles 1-day sick leave (karens only)', () => {
const result = calculateSjuklon(40000, 1, config2026)
expect(result.karensavdrag).toBeGreaterThan(0)
expect(result.sjuklon).toBe(0) // No sjuklön for day 1
})
it('caps at 13 sjuklön days (day 2-14)', () => {
const result14 = calculateSjuklon(40000, 14, config2026)
const result20 = calculateSjuklon(40000, 20, config2026)
// sjuklön should be the same for 14 and 20 days (capped at day 14)
expect(result14.sjuklon).toBe(result20.sjuklon)
})
})
describe('calculateAvgifterRate', () => {
it('returns standard rate for normal employee', () => {
const result = calculateAvgifterRate(
makeBasicInput(),
config2026,
2026
)
expect(result.rate).toBe(0.3142)
expect(result.category).toBe('standard')
})
it('returns reduced rate for 67+ employee', () => {
const result = calculateAvgifterRate(
makeBasicInput({ personnummer: 'mock_senior_person' }),
config2026,
2026
)
expect(result.rate).toBe(0.1021)
expect(result.category).toBe('reduced_65plus')
})
it('returns 0% for born ≤1937', () => {
const result = calculateAvgifterRate(
makeBasicInput({ personnummer: 'mock_old_person' }),
config2026,
2026
)
expect(result.rate).toBe(0)
expect(result.category).toBe('exempt')
})
it('returns växa-stöd rate when eligible', () => {
const result = calculateAvgifterRate(
makeBasicInput({
vaxaStodEligible: true,
vaxaStodStart: '2025-01-01',
vaxaStodEnd: '2026-12-31',
}),
config2026,
2026
)
expect(result.rate).toBe(0.1021)
expect(result.category).toBe('vaxa_stod')
})
// Ungdomsrabatt 2026-2027 (Prop. 2025/26:66). Eligibility test is
// age >= 18 AND age < 23 at årets ingång. Cases below pin all four age
// boundaries plus the period-window edges.
describe('youth rate (ungdomsrabatt 2026-2027)', () => {
it('NOT eligible: age 17 at year start (too young)', () => {
const result = calculateAvgifterRate(
makeBasicInput({ personnummer: 'mock_born_2009', paymentDate: '2026-05-25' }),
config2026,
2026,
)
expect(result.category).toBe('standard')
expect(result.rate).toBe(0.3142)
})
it('eligible: age 18 at year start (lower boundary)', () => {
const result = calculateAvgifterRate(
makeBasicInput({ personnummer: 'mock_born_2008', paymentDate: '2026-05-25' }),
config2026,
2026,
)
expect(result.category).toBe('youth')
expect(result.rate).toBe(0.2081)
})
it('eligible: age 22 at year start (upper boundary)', () => {
const result = calculateAvgifterRate(
makeBasicInput({ personnummer: 'mock_born_2004', paymentDate: '2026-05-25' }),
config2026,
2026,
)
expect(result.category).toBe('youth')
expect(result.rate).toBe(0.2081)
})
// Regression: this is the case Skatteverket's AGI validator rejected.
// The previous implementation incorrectly accepted age 23 at year start.
it('NOT eligible: age 23 at year start (just over)', () => {
const result = calculateAvgifterRate(
makeBasicInput({ personnummer: 'mock_born_2003', paymentDate: '2026-05-25' }),
config2026,
2026,
)
expect(result.category).toBe('standard')
expect(result.rate).toBe(0.3142)
})
it('NOT eligible: age 22 but paid March 2026 (before period starts)', () => {
const result = calculateAvgifterRate(
makeBasicInput({ personnummer: 'mock_born_2004', paymentDate: '2026-03-15' }),
config2026,
2026,
)
expect(result.category).toBe('standard')
expect(result.rate).toBe(0.3142)
})
it('NOT eligible: age 22 but paid October 2027 (after period ends)', () => {
const config2027: PayrollConfig = { ...config2026, configYear: 2027 }
const result = calculateAvgifterRate(
makeBasicInput({ personnummer: 'mock_born_2005', paymentDate: '2027-10-10' }),
config2027,
2027,
)
expect(result.category).toBe('standard')
expect(result.rate).toBe(0.3142)
})
it('eligible: payment exactly April 1 2026 (period start edge)', () => {
const result = calculateAvgifterRate(
makeBasicInput({ personnummer: 'mock_born_2004', paymentDate: '2026-04-01' }),
config2026,
2026,
)
expect(result.category).toBe('youth')
expect(result.rate).toBe(0.2081)
})
it('eligible: payment exactly September 30 2027 (period end edge)', () => {
const config2027: PayrollConfig = { ...config2026, configYear: 2027 }
const result = calculateAvgifterRate(
makeBasicInput({ personnummer: 'mock_born_2005', paymentDate: '2027-09-30' }),
config2027,
2027,
)
expect(result.category).toBe('youth')
expect(result.rate).toBe(0.2081)
})
})
})
describe('calculateSalary: youth cap', () => {
// The 25 000 SEK monthly cap is applied by calculateSalary (not
// calculateAvgifterRate) so it has to be exercised through the integration
// path. Salary above the cap: discounted portion at 20.81%, excess at 31.42%.
it('applies 20.81% on first 25 000 SEK and 31.42% on the excess', () => {
const result = calculateSalary(
makeBasicInput({
personnummer: 'mock_born_2004', // age 22 at year start 2026
paymentDate: '2026-06-25',
monthlySalary: 30000,
}),
config2026,
[],
)
// 25 000 × 0.2081 + 5 000 × 0.3142 = 5 202.50 + 1 571.00 = 6 773.50
expect(result.avgifterAmount).toBeCloseTo(6773.5, 1)
expect(result.avgifterCategory).toBe('youth')
})
it('applies pure 20.81% when salary is at or below the cap', () => {
const result = calculateSalary(
makeBasicInput({
personnummer: 'mock_born_2004',
paymentDate: '2026-06-25',
monthlySalary: 20000,
}),
config2026,
[],
)
// 20 000 × 0.2081 = 4 162.00
expect(result.avgifterAmount).toBeCloseTo(4162, 1)
expect(result.avgifterCategory).toBe('youth')
})
})
describe('calculateSalary: shift premiums (OB-tillägg och övertid)', () => {
it('treats ob_weekend as an addition to gross salary', () => {
const result = calculateSalary(
makeBasicInput({
monthlySalary: 40000,
lineItems: [
baseLineItem(40000),
lineItem({
itemType: 'ob_weekend',
amount: 660,
isTaxable: true,
isAvgiftBasis: true,
isVacationBasis: true,
}),
],
}),
config2026,
emptyTaxRates,
)
// Gross = base 40000 + 660 OB
expect(result.grossSalary).toBe(40660)
// Avgifter basis includes the OB amount
expect(result.avgifterBasis).toBe(40660)
})
it('overtime_50 + ob_night flow into additions step', () => {
const result = calculateSalary(
makeBasicInput({
monthlySalary: 40000,
lineItems: [
baseLineItem(40000),
lineItem({
itemType: 'overtime_50',
amount: 1500,
isTaxable: true,
isAvgiftBasis: true,
isVacationBasis: true,
}),
lineItem({
itemType: 'ob_night',
amount: 900,
isTaxable: true,
isAvgiftBasis: true,
isVacationBasis: true,
}),
],
}),
config2026,
emptyTaxRates,
)
// Gross = 40000 + 1500 + 900 = 42400
expect(result.grossSalary).toBe(42400)
expect(result.avgifterBasis).toBe(42400)
// Should label step as additions including OB
const additionStep = result.steps.find((s) => s.label.includes('Tillägg'))
expect(additionStep).toBeDefined()
expect(additionStep?.output).toBe(2400)
})
})