react-calendar/src/shared/dates.spec.ts

Ultimate calendar for your React app.

import { describe, expect, it } from 'vitest';
import { getDayStart, getDayEnd } from '@wojtekmaj/date-utils';

import {
  getDayOfWeek,
  getBeginOfCenturyYear,
  getBeginOfDecadeYear,
  getBeginOfWeek,
  getWeekNumber,
  getRange,
  getBegin,
  getBeginPrevious,
  getBeginNext,
  getBeginPrevious2,
  getBeginNext2,
  getEnd,
  getEndPrevious,
  getEndPrevious2,
  getValueRange,
  getCenturyLabel,
  getDecadeLabel,
  isWeekend,
} from './dates.js';

describe('getDayOfWeek', () => {
  it('returns proper day of the week (ISO 8601)', () => {
    const date = new Date(2017, 0, 1);

    const dayOfWeek = getDayOfWeek(date, 'iso8601');

    expect(dayOfWeek).toBe(6);
  });

  it('returns proper day of the week (US)', () => {
    const date = new Date(2017, 0, 1);

    const dayOfWeek = getDayOfWeek(date, 'gregory');

    expect(dayOfWeek).toBe(0);
  });

  it('returns proper day of the week (Islamic)', () => {
    const date = new Date(2017, 0, 1);

    const dayOfWeek = getDayOfWeek(date, 'islamic');

    expect(dayOfWeek).toBe(1);
  });

  it('returns proper day of the week (Hebrew)', () => {
    const date = new Date(2017, 0, 1);

    const dayOfWeek = getDayOfWeek(date, 'hebrew');

    expect(dayOfWeek).toBe(0);
  });

  it('returns proper day of the week (default)', () => {
    const date = new Date(2017, 0, 1);

    const dayOfWeek = getDayOfWeek(date);

    expect(dayOfWeek).toBe(6);
  });

  it('throws an error when given unrecognized calendar type', () => {
    const date = new Date(2017, 0, 1);

    // @ts-expect-error-next-line
    expect(() => getDayOfWeek(date, 'Chinese')).toThrow();
  });
});

describe('getBeginOfCenturyYear', () => {
  it('returns proper year of the beginning of the century', () => {
    const date1 = new Date(2017, 0, 1);
    const date2 = new Date(2001, 0, 1);
    const date3 = new Date(2000, 0, 1);

    const beginOfCenturyYear1 = getBeginOfCenturyYear(date1);
    const beginOfCenturyYear2 = getBeginOfCenturyYear(date2);
    const beginOfCenturyYear3 = getBeginOfCenturyYear(date3);

    expect(beginOfCenturyYear1).toBe(2001);
    expect(beginOfCenturyYear2).toBe(2001);
    expect(beginOfCenturyYear3).toBe(1901);
  });
});

describe('getBeginOfDecadeYear', () => {
  it('returns proper year of the beginning of the decade', () => {
    const date1 = new Date(2017, 0, 1);
    const date2 = new Date(2001, 0, 1);
    const date3 = new Date(2000, 0, 1);

    const beginOfDecadeYear1 = getBeginOfDecadeYear(date1);
    const beginOfDecadeYear2 = getBeginOfDecadeYear(date2);
    const beginOfDecadeYear3 = getBeginOfDecadeYear(date3);

    expect(beginOfDecadeYear1).toBe(2011);
    expect(beginOfDecadeYear2).toBe(2001);
    expect(beginOfDecadeYear3).toBe(1991);
  });
});

describe('getBeginOfWeek', () => {
  it('returns proper beginning of the week (ISO 8601)', () => {
    const date = new Date(2017, 0, 1);
    const beginOfWeekDate = new Date(2016, 11, 26);

    const beginOfWeek = getBeginOfWeek(date, 'iso8601');

    expect(beginOfWeek).toEqual(beginOfWeekDate);
  });

  it('returns proper beginning of the week (US)', () => {
    const date = new Date(2016, 0, 1);
    const beginOfWeekDate = new Date(2015, 11, 27);

    const beginOfWeek = getBeginOfWeek(date, 'gregory');

    expect(beginOfWeek).toEqual(beginOfWeekDate);
  });

  it('returns proper beginning of the week (Islamic)', () => {
    const date = new Date(2016, 0, 1);
    const beginOfWeekDate = new Date(2015, 11, 26);

    const beginOfWeek = getBeginOfWeek(date, 'islamic');

    expect(beginOfWeek).toEqual(beginOfWeekDate);
  });

  it('returns proper beginning of the week (Hebrew)', () => {
    const date = new Date(2016, 0, 1);
    const beginOfWeekDate = new Date(2015, 11, 27);

    const beginOfWeek = getBeginOfWeek(date, 'hebrew');

    expect(beginOfWeek).toEqual(beginOfWeekDate);
  });

  it('returns proper beginning of the week (default)', () => {
    const date = new Date(2017, 0, 1);
    const beginOfWeekDate = new Date(2016, 11, 26);

    const beginOfWeek = getBeginOfWeek(date);

    expect(beginOfWeek).toEqual(beginOfWeekDate);
  });
});

describe('getWeekNumber', () => {
  it('returns proper week number for a sample week 1 (ISO 8601)', () => {
    const year = 2018;
    const month = 0;
    const startDate = 1;

    for (let currentDate = startDate; currentDate < startDate + 7; currentDate += 1) {
      const date = new Date(year, month, currentDate);

      const weekNumber = getWeekNumber(date, 'iso8601');

      expect(weekNumber).toBe(1);
    }
  });

  it('returns proper week number for a sample year starting in week 1 (ISO 8601)', () => {
    const year = 2018;
    const month = 0;
    const startDate = 1;

    for (let currentWeek = 1; currentWeek <= 52; currentWeek += 1) {
      const weekOffset = (currentWeek - 1) * 7;
      const date = new Date(year, month, startDate + weekOffset);

      const weekNumber = getWeekNumber(date, 'iso8601');

      expect(weekNumber).toBe(currentWeek);
    }
  });

  it('returns proper week number for a sample week 52 (ISO 8601)', () => {
    const year = 2016;
    const month = 11;
    const startDate = 26;

    for (let currentDate = startDate; currentDate < startDate + 7; currentDate += 1) {
      const date = new Date(year, month, currentDate);

      const weekNumber = getWeekNumber(date, 'iso8601');

      expect(weekNumber).toBe(52);
    }
  });

  it('returns proper week number for a sample week 53 (ISO 8601)', () => {
    const year = 2015;
    const month = 11;
    const startDate = 28;

    for (let currentDate = startDate; currentDate < startDate + 7; currentDate += 1) {
      const date = new Date(year, month, currentDate);

      const weekNumber = getWeekNumber(date, 'iso8601');

      expect(weekNumber).toBe(53);
    }
  });

  it('returns proper week number for a sample week 1 (US)', () => {
    const year = 2015;
    const month = 11;
    const startDate = 27;

    for (let currentDate = startDate; currentDate < startDate + 7; currentDate += 1) {
      const date = new Date(year, month, currentDate);

      const weekNumber = getWeekNumber(date, 'gregory');

      expect(weekNumber).toBe(1);
    }
  });

  it('returns proper week number for a sample year starting in week 1 (US)', () => {
    const year = 2016;
    const month = 0;
    const startDate = 1;

    for (let currentWeek = 1; currentWeek <= 53; currentWeek += 1) {
      const weekOffset = (currentWeek - 1) * 7;
      const date = new Date(year, month, startDate + weekOffset);

      const weekNumber = getWeekNumber(date, 'gregory');

      expect(weekNumber).toBe(currentWeek);
    }
  });

  it('returns proper week number for a sample week 52 (US)', () => {
    const year = 2017;
    const month = 11;
    const startDate = 24;

    for (let currentDate = startDate; currentDate < startDate + 7; currentDate += 1) {
      const date = new Date(year, month, currentDate);

      const weekNumber = getWeekNumber(date, 'gregory');

      expect(weekNumber).toBe(52);
    }
  });

  it('returns proper week number for a sample week 53 (US)', () => {
    const year = 2016;
    const month = 11;
    const startDate = 25;

    for (let currentDate = startDate; currentDate < startDate + 7; currentDate += 1) {
      const date = new Date(year, month, currentDate);

      const weekNumber = getWeekNumber(date, 'gregory');

      expect(weekNumber).toBe(53);
    }
  });

  it('returns proper week number for a sample week 1 (Hebrew)', () => {
    const year = 2017;
    const month = 0;
    const startDate = 1;

    for (let currentDate = startDate; currentDate < startDate + 7; currentDate += 1) {
      const date = new Date(year, month, currentDate);

      const weekNumber = getWeekNumber(date, 'hebrew');

      expect(weekNumber).toBe(1);
    }
  });

  it('returns proper week number for a sample year starting in week 1 (Hebrew)', () => {
    const year = 2018;
    const month = 0;
    const startDate = 1;

    for (let currentWeek = 1; currentWeek <= 52; currentWeek += 1) {
      const weekOffset = (currentWeek - 1) * 7;
      const date = new Date(year, month, startDate + weekOffset);

      const weekNumber = getWeekNumber(date, 'hebrew');

      expect(weekNumber).toBe(currentWeek);
    }
  });

  it('returns proper week number for a sample week 52 (Hebrew)', () => {
    const year = 2016;
    const month = 11;
    const startDate = 25;

    for (let currentDate = startDate; currentDate < startDate + 7; currentDate += 1) {
      const date = new Date(year, month, currentDate);

      const weekNumber = getWeekNumber(date, 'hebrew');

      expect(weekNumber).toBe(52);
    }
  });

  it('returns proper week number for a sample week 53 (Hebrew)', () => {
    const year = 2014;
    const month = 11;
    const startDate = 28;

    for (let currentDate = startDate; currentDate < startDate + 7; currentDate += 1) {
      const date = new Date(year, month, currentDate);

      const weekNumber = getWeekNumber(date, 'hebrew');

      expect(weekNumber).toBe(53);
    }
  });

  it('returns proper week number for a sample week 1 (Islamic)', () => {
    const year = 2022;
    const month = 0;
    const startDate = 1;

    for (let currentDate = startDate; currentDate < startDate + 7; currentDate += 1) {
      const date = new Date(year, month, currentDate);

      const weekNumber = getWeekNumber(date, 'islamic');

      expect(weekNumber).toBe(1);
    }
  });

  it('returns proper week number for a sample year starting in week 1 (Islamic)', () => {
    const year = 2018;
    const month = 0;
    const startDate = 1;

    for (let currentWeek = 1; currentWeek <= 52; currentWeek += 1) {
      const weekOffset = (currentWeek - 1) * 7;
      const date = new Date(year, month, startDate + weekOffset);

      const weekNumber = getWeekNumber(date, 'islamic');

      expect(weekNumber).toBe(currentWeek);
    }
  });

  it('returns proper week number for a sample week 52 (Islamic)', () => {
    const year = 2020;
    const month = 11;
    const startDate = 26;

    for (let currentDate = startDate; currentDate < startDate + 7; currentDate += 1) {
      const date = new Date(year, month, currentDate);

      const weekNumber = getWeekNumber(date, 'islamic');

      expect(weekNumber).toBe(52);
    }
  });

  it('returns proper week number for a sample week 53 (Islamic)', () => {
    const year = 2019;
    const month = 11;
    const startDate = 28;

    for (let currentDate = startDate; currentDate < startDate + 7; currentDate += 1) {
      const date = new Date(year, month, currentDate);

      const weekNumber = getWeekNumber(date, 'islamic');

      expect(weekNumber).toBe(53);
    }
  });
});

describe('getRange', () => {
  it('returns proper century range', () => {
    const date = new Date(2017, 0, 1);
    const beginOfCenturyDate = new Date(2001, 0, 1);
    const endOfCenturyDate = new Date(2100, 11, 31, 23, 59, 59, 999);

    const centuryRange = getRange('century', date);

    expect(centuryRange).toHaveLength(2);
    expect(centuryRange).toEqual([beginOfCenturyDate, endOfCenturyDate]);
  });

  it('returns proper decade range', () => {
    const date = new Date(2017, 0, 1);
    const beginOfDecadeDate = new Date(2011, 0, 1);
    const endOfDecadeDate = new Date(2020, 11, 31, 23, 59, 59, 999);

    const decadeRange = getRange('decade', date);

    expect(decadeRange).toHaveLength(2);
    expect(decadeRange).toEqual([beginOfDecadeDate, endOfDecadeDate]);
  });

  it('returns proper year range', () => {
    const date = new Date(2017, 0, 1);
    const beginOfYearDate = new Date(2017, 0, 1);
    const endOfYearDate = new Date(2017, 11, 31, 23, 59, 59, 999);

    const yearRange = getRange('year', date);

    expect(yearRange).toHaveLength(2);
    expect(yearRange).toEqual([beginOfYearDate, endOfYearDate]);
  });

  it('returns proper month range', () => {
    const date = new Date(2017, 0, 1);
    const beginOfMonthDate = new Date(2017, 0, 1);
    const endOfMonthDate = new Date(2017, 0, 31, 23, 59, 59, 999);

    const monthRange = getRange('month', date);

    expect(monthRange).toHaveLength(2);
    expect(monthRange).toEqual([beginOfMonthDate, endOfMonthDate]);
  });

  it('returns proper day range', () => {
    const date = new Date(2017, 0, 1);
    const beginOfDayDate = new Date(2017, 0, 1);
    const endOfDayDate = new Date(2017, 0, 1, 23, 59, 59, 999);

    const dayRange = getRange('day', date);

    expect(dayRange).toHaveLength(2);
    expect(dayRange).toEqual([beginOfDayDate, endOfDayDate]);
  });

  it('throws an error when given unrecognized range type', () => {
    const date = new Date(2017, 0, 1);

    // @ts-expect-error-next-line
    expect(() => getRange('hamster', date)).toThrow();
  });
});

describe('getBegin', () => {
  it('returns proper beginning of the century', () => {
    const date = new Date(2017, 0, 1);
    const beginOfCenturyDate = new Date(2001, 0, 1);

    const beginOfCentury = getBegin('century', date);

    expect(beginOfCentury).toEqual(beginOfCenturyDate);
  });

  it('returns proper beginning of the decade', () => {
    const date = new Date(2017, 0, 1);
    const beginOfDecadeDate = new Date(2011, 0, 1);

    const beginOfDecade = getBegin('decade', date);

    expect(beginOfDecade).toEqual(beginOfDecadeDate);
  });

  it('returns proper beginning of the year', () => {
    const date = new Date(2017, 0, 1);
    const beginOfYearDate = new Date(2017, 0, 1);

    const beginOfYear = getBegin('year', date);

    expect(beginOfYear).toEqual(beginOfYearDate);
  });

  it('returns proper beginning of the month', () => {
    const date = new Date(2017, 0, 1);
    const beginOfMonthDate = new Date(2017, 0, 1);

    const monthRange = getBegin('month', date);

    expect(monthRange).toEqual(beginOfMonthDate);
  });

  it('returns proper beginning of the day', () => {
    const date = new Date(2017, 0, 1);
    const beginOfDayDate = new Date(2017, 0, 1);

    const beginOfDay = getBegin('day', date);

    expect(beginOfDay).toEqual(beginOfDayDate);
  });

  it('throws an error when given unrecognized range type', () => {
    const date = new Date(2017, 0, 1);

    // @ts-expect-error-next-line
    expect(() => getBegin('hamster', date)).toThrow();
  });
});

describe('getBeginPrevious', () => {
  it('returns proper beginning of the previous century', () => {
    const date = new Date(2017, 0, 1);
    const beginOfCenturyDate = new Date(1901, 0, 1);

    const beginOfCentury = getBeginPrevious('century', date);

    expect(beginOfCentury).toEqual(beginOfCenturyDate);
  });

  it('returns proper beginning of the previous decade', () => {
    const date = new Date(2017, 0, 1);
    const beginOfDecadeDate = new Date(2001, 0, 1);

    const beginOfDecade = getBeginPrevious('decade', date);

    expect(beginOfDecade).toEqual(beginOfDecadeDate);
  });

  it('returns proper beginning of the previous year', () => {
    const date = new Date(2017, 0, 1);
    const beginOfYearDate = new Date(2016, 0, 1);

    const beginOfYear = getBeginPrevious('year', date);

    expect(beginOfYear).toEqual(beginOfYearDate);
  });

  it('returns proper beginning of the previous month', () => {
    const date = new Date(2017, 0, 1);
    const beginOfMonthDate = new Date(2016, 11, 1);

    const monthRange = getBeginPrevious('month', date);

    expect(monthRange).toEqual(beginOfMonthDate);
  });

  it('throws an error when given unrecognized range type', () => {
    const date = new Date(2017, 0, 1);

    // @ts-expect-error-next-line
    expect(() => getBeginPrevious('hamster', date)).toThrow();
  });
});

describe('getBeginNext', () => {
  it('returns proper beginning of the next century', () => {
    const date = new Date(2017, 0, 1);
    const beginOfCenturyDate = new Date(2101, 0, 1);

    const beginOfCentury = getBeginNext('century', date);

    expect(beginOfCentury).toEqual(beginOfCenturyDate);
  });

  it('returns proper beginning of the next decade', () => {
    const date = new Date(2017, 0, 1);
    const beginOfDecadeDate = new Date(2021, 0, 1);

    const beginOfDecade = getBeginNext('decade', date);

    expect(beginOfDecade).toEqual(beginOfDecadeDate);
  });

  it('returns proper beginning of the next year', () => {
    const date = new Date(2017, 0, 1);
    const beginOfYearDate = new Date(2018, 0, 1);

    const beginOfYear = getBeginNext('year', date);

    expect(beginOfYear).toEqual(beginOfYearDate);
  });

  it('returns proper beginning of the next month', () => {
    const date = new Date(2017, 0, 1);
    const beginOfMonthDate = new Date(2017, 1, 1);

    const monthRange = getBeginNext('month', date);

    expect(monthRange).toEqual(beginOfMonthDate);
  });

  it('throws an error when given unrecognized range type', () => {
    const date = new Date(2017, 0, 1);

    // @ts-expect-error-next-line
    expect(() => getBeginNext('hamster', date)).toThrow();
  });
});

describe('getBeginPrevious2', () => {
  it('returns proper beginning of the decade 10 decades ago', () => {
    const date = new Date(2017, 0, 1);
    const beginOfPreviousCenturyDate = new Date(1911, 0, 1);

    const beginOfPreviousCentury = getBeginPrevious2('decade', date);

    expect(beginOfPreviousCentury).toEqual(beginOfPreviousCenturyDate);
  });

  it('returns proper beginning of the year 10 years ago', () => {
    const date = new Date(2017, 0, 1);
    const beginOfPreviousDecadeDate = new Date(2007, 0, 1);

    const beginOfPreviousDecade = getBeginPrevious2('year', date);

    expect(beginOfPreviousDecade).toEqual(beginOfPreviousDecadeDate);
  });

  it('returns proper beginning of the month 1 year ago', () => {
    const date = new Date(2017, 0, 1);
    const beginOfPreviousYearDate = new Date(2016, 0, 1);

    const beginOfPreviousYear = getBeginPrevious2('month', date);

    expect(beginOfPreviousYear).toEqual(beginOfPreviousYearDate);
  });

  it('throws an error when given unrecognized range type', () => {
    const date = new Date(2017, 0, 1);

    // @ts-expect-error-next-line
    expect(() => getBeginPrevious2('hamster', date)).toThrow();
  });
});

describe('getBeginNext2', () => {
  it('returns proper beginning of the decade 10 decades ahead', () => {
    const date = new Date(2017, 0, 1);
    const beginOfNextCenturyDate = new Date(2111, 0, 1);

    const beginOfNextCentury = getBeginNext2('decade', date);

    expect(beginOfNextCentury).toEqual(beginOfNextCenturyDate);
  });

  it('returns proper beginning of the year 10 years ahead', () => {
    const date = new Date(2017, 0, 1);
    const beginOfNextDecadeDate = new Date(2027, 0, 1);

    const beginOfNextDecade = getBeginNext2('year', date);

    expect(beginOfNextDecade).toEqual(beginOfNextDecadeDate);
  });

  it('returns proper beginning of the month 1 year ahead', () => {
    const date = new Date(2017, 0, 1);
    const beginOfNextYearDate = new Date(2018, 0, 1);

    const beginOfNextYear = getBeginNext2('month', date);

    expect(beginOfNextYear).toEqual(beginOfNextYearDate);
  });

  it('throws an error when given unrecognized range type', () => {
    const date = new Date(2017, 0, 1);

    // @ts-expect-error-next-line
    expect(() => getBeginNext2('hamster', date)).toThrow();
  });
});

describe('getEnd', () => {
  it('returns proper end of the century', () => {
    const date = new Date(2017, 0, 1);
    const endOfCenturyDate = new Date(2100, 11, 31, 23, 59, 59, 999);

    const endOfCentury = getEnd('century', date);

    expect(endOfCentury).toEqual(endOfCenturyDate);
  });

  it('returns proper end of the decade', () => {
    const date = new Date(2017, 0, 1);
    const endOfDecadeDate = new Date(2020, 11, 31, 23, 59, 59, 999);

    const endOfDecade = getEnd('decade', date);

    expect(endOfDecade).toEqual(endOfDecadeDate);
  });

  it('returns proper end of the year', () => {
    const date = new Date(2017, 0, 1);
    const endOfYearDate = new Date(2017, 11, 31, 23, 59, 59, 999);

    const endOfYear = getEnd('year', date);

    expect(endOfYear).toEqual(endOfYearDate);
  });

  it('returns proper end of the month', () => {
    const date = new Date(2017, 0, 1);
    const endOfMonthDate = new Date(2017, 0, 31, 23, 59, 59, 999);

    const monthRange = getEnd('month', date);

    expect(monthRange).toEqual(endOfMonthDate);
  });

  it('returns proper end of the day', () => {
    const date = new Date(2017, 0, 1);
    const endOfDayDate = new Date(2017, 0, 1, 23, 59, 59, 999);

    const endOfDay = getEnd('day', date);

    expect(endOfDay).toEqual(endOfDayDate);
  });

  it('throws an error when given unrecognized range type', () => {
    const date = new Date(2017, 0, 1);

    // @ts-expect-error-next-line
    expect(() => getEnd('hamster', date)).toThrow();
  });
});

describe('getEndPrevious', () => {
  it('returns proper end of the previous century', () => {
    const date = new Date(2017, 0, 1);
    const endOfCenturyDate = new Date(2000, 11, 31, 23, 59, 59, 999);

    const endOfCentury = getEndPrevious('century', date);

    expect(endOfCentury).toEqual(endOfCenturyDate);
  });

  it('returns proper end of the previous decade', () => {
    const date = new Date(2017, 0, 1);
    const endOfDecadeDate = new Date(2010, 11, 31, 23, 59, 59, 999);

    const endOfDecade = getEndPrevious('decade', date);

    expect(endOfDecade).toEqual(endOfDecadeDate);
  });

  it('returns proper end of the previous year', () => {
    const date = new Date(2017, 0, 1);
    const endOfYearDate = new Date(2016, 11, 31, 23, 59, 59, 999);

    const endOfYear = getEndPrevious('year', date);

    expect(endOfYear).toEqual(endOfYearDate);
  });

  it('returns proper end of the previous month', () => {
    const date = new Date(2017, 0, 1);
    const endOfMonthDate = new Date(2016, 11, 31, 23, 59, 59, 999);

    const monthRange = getEndPrevious('month', date);

    expect(monthRange).toEqual(endOfMonthDate);
  });

  it('throws an error when given unrecognized range type', () => {
    const date = new Date(2017, 0, 1);

    // @ts-expect-error-next-line
    expect(() => getEndPrevious('hamster', date)).toThrow();
  });
});

describe('getEndPrevious2', () => {
  it('returns proper end of the decade 10 decades ago', () => {
    const date = new Date(2017, 0, 1);
    const endOfPreviousCenturyDate = new Date(1920, 11, 31, 23, 59, 59, 999);

    const endOfPreviousCentury = getEndPrevious2('decade', date);

    expect(endOfPreviousCentury).toEqual(endOfPreviousCenturyDate);
  });

  it('returns proper end of the year 10 years ago', () => {
    const date = new Date(2017, 0, 1);
    const endOfPreviousDecadeDate = new Date(2007, 11, 31, 23, 59, 59, 999);

    const endOfPreviousDecade = getEndPrevious2('year', date);

    expect(endOfPreviousDecade).toEqual(endOfPreviousDecadeDate);
  });

  it('returns proper end of the month 1 year ago', () => {
    const date = new Date(2017, 0, 1);
    const endOfPreviousYearDate = new Date(2016, 0, 31, 23, 59, 59, 999);

    const endOfPreviousYear = getEndPrevious2('month', date);

    expect(endOfPreviousYear).toEqual(endOfPreviousYearDate);
  });

  it('throws an error when given unrecognized range type', () => {
    const date = new Date(2017, 0, 1);

    // @ts-expect-error-next-line
    expect(() => getEndPrevious2('hamster', date)).toThrow();
  });
});

describe('getValueRange', () => {
  it('returns an array of dates given two ordered dates', () => {
    const date1 = new Date(2018, 0, 1);
    const date2 = new Date(2018, 6, 1);

    const range = getValueRange('day', date1, date2);

    expect(range).toEqual([getDayStart(date1), getDayEnd(date2)]);
  });

  it('returns an array of dates given two unordered dates', () => {
    const date1 = new Date(2018, 6, 1);
    const date2 = new Date(2018, 0, 1);

    const range = getValueRange('day', date1, date2);

    expect(range).toEqual([getDayStart(date2), getDayEnd(date1)]);
  });
});

describe('getCenturyLabel', () => {
  it('returns proper label for the century a given date is in', () => {
    const date = new Date(2017, 0, 1);

    const centuryLabel = getCenturyLabel('en-US', undefined, date);

    expect(centuryLabel).toBe('2001 – 2100');
  });
});

describe('getDecadeLabel', () => {
  it('returns proper label for the decade a given date is in', () => {
    const date = new Date(2017, 0, 1);

    const decadeLabel = getDecadeLabel('en-US', undefined, date);

    expect(decadeLabel).toBe('2011 – 2020');
  });
});

describe('isWeekend', () => {
  describe('returns proper flag (ISO 8601)', () => {
    it.each`
      date                      | flag
      ${new Date(2016, 11, 30)} | ${false}
      ${new Date(2016, 11, 31)} | ${true}
      ${new Date(2017, 0, 1)}   | ${true}
      ${new Date(2017, 0, 2)}   | ${false}
    `('returns $flag for $date', ({ date, flag }) => {
      expect(isWeekend(date, 'iso8601')).toBe(flag);
    });
  });

  describe('returns proper flag (Gregory)', () => {
    it.each`
      date                      | flag
      ${new Date(2016, 11, 30)} | ${false}
      ${new Date(2016, 11, 31)} | ${true}
      ${new Date(2017, 0, 1)}   | ${true}
      ${new Date(2017, 0, 2)}   | ${false}
    `('returns $flag for $date', ({ date, flag }) => {
      expect(isWeekend(date, 'gregory')).toBe(flag);
    });
  });

  describe('returns proper flag (Hebrew)', () => {
    it.each`
      date                      | flag
      ${new Date(2016, 11, 30)} | ${true}
      ${new Date(2016, 11, 31)} | ${true}
      ${new Date(2017, 0, 1)}   | ${false}
      ${new Date(2017, 0, 2)}   | ${false}
    `('returns $flag for $date', ({ date, flag }) => {
      expect(isWeekend(date, 'hebrew')).toBe(flag);
    });
  });

  describe('returns proper flag (Islamic)', () => {
    it.each`
      date                      | flag
      ${new Date(2016, 11, 30)} | ${true}
      ${new Date(2016, 11, 31)} | ${true}
      ${new Date(2017, 0, 1)}   | ${false}
      ${new Date(2017, 0, 2)}   | ${false}
    `('returns $flag for $date', ({ date, flag }) => {
      expect(isWeekend(date, 'islamic')).toBe(flag);
    });
  });

  describe('returns proper flag (default)', () => {
    it.each`
      date                      | flag
      ${new Date(2016, 11, 30)} | ${false}
      ${new Date(2016, 11, 31)} | ${true}
      ${new Date(2017, 0, 1)}   | ${true}
      ${new Date(2017, 0, 2)}   | ${false}
    `('returns $flag for $date', ({ date, flag }) => {
      expect(isWeekend(date)).toBe(flag);
    });
  });
});