nepali-date-converter-np/tests/weekday.test.ts

A lightweight TypeScript/JavaScript package for converting dates between Gregorian (AD) and Bikram Sambat (BS) calendar systems with Nepali and English formatting support.

import { getDayOfWeek, BSDate, ADDate } from '../src/index';

describe('Weekday Calculation Tests', () => {
  describe('getDayOfWeek with English locale', () => {
    test('should return correct English weekday for known BS date', () => {
      // 2000-01-01 BS = 1943-04-14 AD = Wednesday
      const bsDate: BSDate = { year: 2000, month: 1, day: 1 };
      const result = getDayOfWeek(bsDate, 'en');
      expect(result).toBe('Wednesday');
    });

    test('should return correct English weekday for known AD date', () => {
      // 1943-04-14 AD = Wednesday
      const adDate: ADDate = { year: 1943, month: 4, day: 14 };
      const result = getDayOfWeek(adDate, 'en');
      expect(result).toBe('Wednesday');
    });

    test('should return all English weekdays correctly', () => {
      const expectedWeekdays = [
        'Sunday', 'Monday', 'Tuesday', 'Wednesday', 
        'Thursday', 'Friday', 'Saturday'
      ];

      // Test a week of dates to ensure all weekdays are covered
      for (let i = 0; i < 7; i++) {
        const adDate: ADDate = { year: 1943, month: 4, day: 14 + i };
        const result = getDayOfWeek(adDate, 'en');
        expect(expectedWeekdays).toContain(result);
      }
    });

    test('should use English as default locale', () => {
      const bsDate: BSDate = { year: 2000, month: 1, day: 1 };
      const result1 = getDayOfWeek(bsDate);
      const result2 = getDayOfWeek(bsDate, 'en');
      expect(result1).toBe(result2);
    });
  });

  describe('getDayOfWeek with Nepali locale', () => {
    test('should return correct Nepali weekday for known BS date', () => {
      // 2000-01-01 BS = 1943-04-14 AD = बुधबार (Wednesday)
      const bsDate: BSDate = { year: 2000, month: 1, day: 1 };
      const result = getDayOfWeek(bsDate, 'ne');
      expect(result).toBe('बुधबार');
    });

    test('should return correct Nepali weekday for known AD date', () => {
      // 1943-04-14 AD = बुधबार (Wednesday)
      const adDate: ADDate = { year: 1943, month: 4, day: 14 };
      const result = getDayOfWeek(adDate, 'ne');
      expect(result).toBe('बुधबार');
    });

    test('should return all Nepali weekdays correctly', () => {
      const expectedWeekdays = [
        'आइतबार', 'सोमबार', 'मंगलबार', 'बुधबार', 
        'बिहीबार', 'शुक्रबार', 'शनिबार'
      ];

      // Test a week of dates to ensure all weekdays are covered
      for (let i = 0; i < 7; i++) {
        const adDate: ADDate = { year: 1943, month: 4, day: 14 + i };
        const result = getDayOfWeek(adDate, 'ne');
        expect(expectedWeekdays).toContain(result);
      }
    });
  });

  describe('Weekday consistency', () => {
    test('should return same weekday for same date regardless of input type', () => {
      const bsDate: BSDate = { year: 2000, month: 1, day: 1 };
      const adDate: ADDate = { year: 1943, month: 4, day: 14 };
      
      const bsWeekday = getDayOfWeek(bsDate, 'en');
      const adWeekday = getDayOfWeek(adDate, 'en');
      
      expect(bsWeekday).toBe(adWeekday);
    });

    test('should maintain weekday consistency across different dates', () => {
      // Test that weekdays follow the correct sequence
      const weekdays = [];
      for (let i = 0; i < 7; i++) {
        const adDate: ADDate = { year: 1943, month: 4, day: 14 + i };
        weekdays.push(getDayOfWeek(adDate, 'en'));
      }
      
      const expectedSequence = ['Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday', 'Monday', 'Tuesday'];
      expect(weekdays).toEqual(expectedSequence);
    });
  });

  describe('Edge cases', () => {
    test('should handle month boundary dates', () => {
      const bsDate: BSDate = { year: 2000, month: 12, day: 31 };
      const result = getDayOfWeek(bsDate, 'en');
      expect(result).toBeDefined();
      expect(typeof result).toBe('string');
      expect(['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday']).toContain(result);
    });

    test('should handle leap year dates', () => {
      const adDate: ADDate = { year: 1944, month: 2, day: 29 };
      const result = getDayOfWeek(adDate, 'en');
      expect(result).toBeDefined();
      expect(typeof result).toBe('string');
      expect(['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday']).toContain(result);
    });

    test('should handle year boundary dates', () => {
      const adDate: ADDate = { year: 1943, month: 12, day: 31 };
      const result = getDayOfWeek(adDate, 'en');
      expect(result).toBeDefined();
      expect(typeof result).toBe('string');
      expect(['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday']).toContain(result);
    });
  });

  describe('Input validation', () => {
    test('should throw error for invalid date object', () => {
      const invalidDate = { year: 2000, month: 13, day: 32 };
      expect(() => getDayOfWeek(invalidDate as BSDate, 'en')).toThrow();
    });

    test('should handle unsupported BS date range gracefully', () => {
      const unsupportedBS: BSDate = { year: 2078, month: 6, day: 24 };
      const result = getDayOfWeek(unsupportedBS, 'en');
      expect(['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday']).toContain(result);
    });

    test('should handle unsupported AD date range gracefully', () => {
      const unsupportedAD: ADDate = { year: 2021, month: 10, day: 10 };
      const result = getDayOfWeek(unsupportedAD, 'en');
      expect(['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday']).toContain(result);
    });
  });

  describe('Locale handling', () => {
    test('should handle both locale types correctly', () => {
      const bsDate: BSDate = { year: 2000, month: 1, day: 1 };
      
      const englishResult = getDayOfWeek(bsDate, 'en');
      const nepaliResult = getDayOfWeek(bsDate, 'ne');
      
      expect(englishResult).toBe('Wednesday');
      expect(nepaliResult).toBe('बुधबार');
      expect(englishResult).not.toBe(nepaliResult);
    });

    test('should handle case sensitivity in locale parameter', () => {
      const bsDate: BSDate = { year: 2000, month: 1, day: 1 };
      
      expect(() => getDayOfWeek(bsDate, 'EN' as any)).toThrow();
      expect(() => getDayOfWeek(bsDate, 'NE' as any)).toThrow();
    });
  });

  describe('Performance and consistency', () => {
    test('should return consistent results for same input', () => {
      const bsDate: BSDate = { year: 2000, month: 1, day: 1 };
      const result1 = getDayOfWeek(bsDate, 'en');
      const result2 = getDayOfWeek(bsDate, 'en');
      expect(result1).toBe(result2);
    });

    test('should handle multiple calls without errors', () => {
      const bsDate: BSDate = { year: 2000, month: 1, day: 1 };
      
      for (let i = 0; i < 100; i++) {
        expect(() => getDayOfWeek(bsDate, 'en')).not.toThrow();
        const result = getDayOfWeek(bsDate, 'en');
        expect(result).toBe('Wednesday');
      }
    });
  });
});