Initial commit

frontend/tests/unit/utils/dates.test.ts

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+import { describe, it, expect } from 'vitest'
+import {
+  formatDateForDisplay,
+  formatDateForInput,
+  parseInputDate,
+  isValidDate,
+  getDayName,
+  getMonthName,
+} from '@/utils/dates'
+
+describe('dates.ts utilities', () => {
+  describe('formatDateForDisplay', () => {
+    it('formats ISO string to Swedish display format', () => {
+      const result = formatDateForDisplay('2026-06-15')
+      expect(result).toBe('15 juni 2026')
+    })
+
+    it('formats Date object to Swedish display format', () => {
+      const date = new Date('2026-06-15T00:00:00Z')
+      const result = formatDateForDisplay(date)
+      expect(result).toBe('15 juni 2026')
+    })
+
+    it('handles January correctly', () => {
+      const result = formatDateForDisplay('2026-01-01')
+      expect(result).toBe('1 januari 2026')
+    })
+
+    it('handles December correctly', () => {
+      const result = formatDateForDisplay('2026-12-25')
+      expect(result).toBe('25 december 2026')
+    })
+
+    it('returns empty string for invalid date', () => {
+      const result = formatDateForDisplay('invalid')
+      expect(result).toBe('')
+    })
+  })
+
+  describe('formatDateForInput', () => {
+    it('formats ISO string to input format', () => {
+      const result = formatDateForInput('2026-06-15')
+      expect(result).toBe('2026-06-15')
+    })
+
+    it('formats Date object to input format', () => {
+      const date = new Date('2026-06-15T00:00:00Z')
+      const result = formatDateForInput(date)
+      expect(result).toBe('2026-06-15')
+    })
+
+    it('pads month and day with zeros', () => {
+      const result = formatDateForInput('2026-01-05')
+      expect(result).toBe('2026-01-05')
+    })
+
+    it('returns empty string for invalid date', () => {
+      const result = formatDateForInput('invalid')
+      expect(result).toBe('')
+    })
+  })
+
+  describe('parseInputDate', () => {
+    it('parses ISO date string to Date object', () => {
+      const result = parseInputDate('2026-06-15')
+      expect(result).toBeInstanceOf(Date)
+      expect(result.toISOString()).toContain('2026-06-15')
+    })
+
+    it('creates valid Date for valid input', () => {
+      const result = parseInputDate('2026-06-15')
+      expect(isValidDate(result)).toBe(true)
+    })
+  })
+
+  describe('isValidDate', () => {
+    it('returns true for valid Date object', () => {
+      const date = new Date('2026-06-15')
+      expect(isValidDate(date)).toBe(true)
+    })
+
+    it('returns false for invalid Date', () => {
+      const date = new Date('invalid')
+      expect(isValidDate(date)).toBe(false)
+    })
+
+    it('returns false for non-Date values', () => {
+      expect(isValidDate('2026-06-15')).toBe(false)
+      expect(isValidDate(20260615)).toBe(false)
+      expect(isValidDate(null)).toBe(false)
+      expect(isValidDate(undefined)).toBe(false)
+    })
+  })
+
+  describe('getDayName', () => {
+    it('returns Swedish day name', () => {
+      const date = new Date('2026-06-15T00:00:00Z') // Monday
+      const result = getDayName(date)
+      expect(result.toLowerCase()).toBe('måndag')
+    })
+
+    it('returns empty string for invalid date', () => {
+      const result = getDayName(new Date('invalid'))
+      expect(result).toBe('')
+    })
+  })
+
+  describe('getMonthName', () => {
+    it('returns Swedish month name', () => {
+      const date = new Date('2026-06-15T00:00:00Z')
+      const result = getMonthName(date)
+      expect(result).toBe('juni')
+    })
+
+    it('returns correct month names for all months', () => {
+      const monthNames = [
+        'januari',
+        'februari',
+        'mars',
+        'april',
+        'maj',
+        'juni',
+        'juli',
+        'augusti',
+        'september',
+        'oktober',
+        'november',
+        'december',
+      ]
+
+      monthNames.forEach((monthName, index) => {
+        const date = new Date(`2026-${String(index + 1).padStart(2, '0')}-15T00:00:00Z`)
+        const result = getMonthName(date)
+        expect(result).toBe(monthName)
+      })
+    })
+
+    it('returns empty string for invalid date', () => {
+      const result = getMonthName(new Date('invalid'))
+      expect(result).toBe('')
+    })
+  })
+})

frontend/tests/unit/utils/formatting.test.ts

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+import { describe, it, expect } from 'vitest'
+import { formatDayCount, formatPercentage } from '@/utils/formatting'
+
+describe('formatting.ts utilities', () => {
+  describe('formatDayCount', () => {
+    it('returns singular form for 1 day', () => {
+      expect(formatDayCount(1)).toBe('1 dag')
+    })
+
+    it('returns plural form for 0 days', () => {
+      expect(formatDayCount(0)).toBe('0 dagar')
+    })
+
+    it('returns plural form for 2 days', () => {
+      expect(formatDayCount(2)).toBe('2 dagar')
+    })
+
+    it('returns plural form for many days', () => {
+      expect(formatDayCount(25)).toBe('25 dagar')
+      expect(formatDayCount(365)).toBe('365 dagar')
+    })
+
+    it('handles large numbers', () => {
+      expect(formatDayCount(1000)).toBe('1000 dagar')
+    })
+  })
+
+  describe('formatPercentage', () => {
+    it('formats simple percentage', () => {
+      expect(formatPercentage(1, 4)).toBe('25%')
+    })
+
+    it('rounds to nearest integer', () => {
+      expect(formatPercentage(1, 3)).toBe('33%') // 33.333...%
+      expect(formatPercentage(2, 3)).toBe('67%') // 66.666...%
+    })
+
+    it('handles 0% correctly', () => {
+      expect(formatPercentage(0, 10)).toBe('0%')
+    })
+
+    it('handles 100% correctly', () => {
+      expect(formatPercentage(10, 10)).toBe('100%')
+    })
+
+    it('returns 0% when denominator is 0', () => {
+      expect(formatPercentage(5, 0)).toBe('0%')
+    })
+
+    it('handles fractional results with proper rounding', () => {
+      expect(formatPercentage(1, 2)).toBe('50%')
+      expect(formatPercentage(3, 4)).toBe('75%')
+    })
+
+    it('works with large numbers', () => {
+      expect(formatPercentage(500, 1000)).toBe('50%')
+    })
+  })
+})