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Testing Day.js isSameOrAfter Plugin Implementation in iamkun/dayjs

This test suite validates the isSameOrAfter plugin functionality in Day.js, ensuring accurate datetime comparisons across different units of time. The tests verify both exact matches and relative comparisons while maintaining immutability of the original moment objects.
Test Coverage Overview

The test suite provides comprehensive coverage of the isSameOrAfter functionality across multiple time units including years, months, days, hours, minutes, seconds, and milliseconds. Key test cases include:
Exact timestamp matching
Boundary conditions at start/end of time units
Cross-unit comparisons
Invalid date handling
Plural unit name support
Implementation Analysis

The testing approach uses Jest’s test framework with systematic validation of time comparisons. Each test case follows a consistent pattern of comparing moments with various time differences, ensuring both same-time and after-time scenarios are properly handled. The implementation leverages MockDate for consistent datetime testing.
Technical Details

Testing tools and setup:
Jest testing framework
MockDate for date simulation
Day.js core library
isSameOrAfter plugin
Moment comparison utilities
Best Practices Demonstrated

The test suite exemplifies several testing best practices:
Consistent test case organization
Thorough edge case coverage
Clear test descriptions
Proper test isolation with beforeEach/afterEach
Immutability verification
iamkun/dayjs

test/plugin/isSameOrAfter.test.js
            
import MockDate from 'mockdate'
import dayjs from '../../src'
import isSameOrAfter from '../../src/plugin/isSameOrAfter'

dayjs.extend(isSameOrAfter)

beforeEach(() => {
  MockDate.set(new Date())
})

afterEach(() => {
  MockDate.reset()
})

test('is same or after year', () => {
  const m = dayjs(new Date(2011, 1, 2, 3, 4, 5, 6))
  const mCopy = dayjs(m)
  expect(m.isSameOrAfter(dayjs(new Date(2011, 5, 6, 7, 8, 9, 10)), 'year')).toBe(true, 'year match')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 5, 6, 7, 8, 9, 10)), 'years')).toBe(true, 'plural should work')
  expect(m.isSameOrAfter(dayjs(new Date(2012, 5, 6, 7, 8, 9, 10)), 'year')).toBe(false, 'year is later')
  expect(m.isSameOrAfter(dayjs(new Date(2010, 5, 6, 7, 8, 9, 10)), 'year')).toBe(true, 'year is earlier')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 0, 1, 0, 0, 0, 0)), 'year')).toBe(true, 'exact start of year')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 11, 31, 23, 59, 59, 999)), 'year')).toBe(true, 'exact end of year')
  expect(m.isSameOrAfter(dayjs(new Date(2012, 0, 1, 0, 0, 0, 0)), 'year')).toBe(false, 'start of next year')
  expect(m.isSameOrAfter(dayjs(new Date(2010, 11, 31, 23, 59, 59, 999)), 'year')).toBe(true, 'end of previous year')
  expect(m.isSameOrAfter(m, 'year')).toBe(true, 'same moments are in the same year')
  expect(+m).toEqual(+mCopy, 'isSameOrAfter year should not change moment')
})

test('is same or after without units', () => {
  const m = dayjs(new Date(2011, 3, 2, 3, 4, 5, 10))
  const mCopy = dayjs(m)
  expect(m.isSameOrAfter(dayjs(new Date(2012, 3, 2, 3, 5, 5, 10)))).toBe(false, 'year is later')
  expect(m.isSameOrAfter(dayjs(new Date(2010, 3, 2, 3, 3, 5, 10)))).toBe(true, 'year is earlier')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 4, 2, 3, 4, 5, 10)))).toBe(false, 'month is later')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 2, 2, 3, 4, 5, 10)))).toBe(true, 'month is earlier')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 3, 3, 3, 4, 5, 10)))).toBe(false, 'day is later')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 3, 1, 3, 4, 5, 10)))).toBe(true, 'day is earlier')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 3, 2, 4, 4, 5, 10)))).toBe(false, 'hour is later')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 3, 2, 2, 4, 5, 10)))).toBe(true, 'hour is earlier')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 3, 2, 3, 5, 5, 10)))).toBe(false, 'minute is later')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 3, 2, 3, 3, 5, 10)))).toBe(true, 'minute is earlier')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 3, 2, 3, 4, 6, 10)))).toBe(false, 'second is later')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 3, 2, 3, 4, 4, 11)))).toBe(true, 'second is earlier')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 3, 2, 3, 4, 5, 10)))).toBe(true, 'millisecond match')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 3, 2, 3, 4, 5, 11)))).toBe(false, 'millisecond is later')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 3, 2, 3, 4, 5, 9)))).toBe(true, 'millisecond is earlier')
  expect(m.isSameOrAfter(m)).toBe(true, 'moments are the same as themselves')
  expect(+m).toEqual(+mCopy, 'isSameOrAfter second should not change moment')
})

test('is same or after without date', () => {
  const past = dayjs().subtract(1, 'day')
  const future = dayjs().add(1, 'day')
  expect(past.isSameOrAfter()).toBe(false, 'past is before now')
  expect(future.isSameOrAfter()).toBe(true, 'future is not before now')
})

test('is same or after month', () => {
  const m = dayjs(new Date(2011, 2, 3, 4, 5, 6, 7))
  const mCopy = dayjs(m)
  expect(m.isSameOrAfter(dayjs(new Date(2011, 2, 6, 7, 8, 9, 10)), 'month')).toBe(true, 'month match')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 2, 6, 7, 8, 9, 10)), 'months')).toBe(true, 'plural should work')
  expect(m.isSameOrAfter(dayjs(new Date(2012, 2, 6, 7, 8, 9, 10)), 'month')).toBe(false, 'year is later')
  expect(m.isSameOrAfter(dayjs(new Date(2010, 2, 6, 7, 8, 9, 10)), 'month')).toBe(true, 'year is earlier')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 5, 6, 7, 8, 9, 10)), 'month')).toBe(false, 'month is later')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 6, 7, 8, 9, 10)), 'month')).toBe(true, 'month is earlier')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 2, 1, 0, 0, 0, 0)), 'month')).toBe(true, 'exact start of month')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 2, 31, 23, 59, 59, 999)), 'month')).toBe(true, 'exact end of month')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 3, 1, 0, 0, 0, 0)), 'month')).toBe(false, 'start of next month')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 27, 23, 59, 59, 999)), 'month')).toBe(true, 'end of previous month')
  expect(m.isSameOrAfter(m, 'month')).toBe(true, 'same moments are in the same month')
  expect(+m).toEqual(+mCopy, 'isSameOrAfter month should not change moment')
})

test('is same or after day', () => {
  const m = dayjs(new Date(2011, 1, 2, 3, 4, 5, 6))
  const mCopy = dayjs(m)
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 7, 8, 9, 10)), 'day')).toBe(true, 'day match')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 7, 8, 9, 10)), 'days')).toBe(true, 'plural should work')
  expect(m.isSameOrAfter(dayjs(new Date(2012, 1, 2, 7, 8, 9, 10)), 'day')).toBe(false, 'year is later')
  expect(m.isSameOrAfter(dayjs(new Date(2010, 1, 2, 7, 8, 9, 10)), 'day')).toBe(true, 'year is earlier')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 2, 2, 7, 8, 9, 10)), 'day')).toBe(false, 'month is later')
  expect(m.isSameOrAfter(dayjs(new Date(2010, 12, 2, 7, 8, 9, 10)), 'day')).toBe(true, 'month is earlier')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 3, 7, 8, 9, 10)), 'day')).toBe(false, 'day is later')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 1, 7, 8, 9, 10)), 'day')).toBe(true, 'day is earlier')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 0, 0, 0, 0)), 'day')).toBe(true, 'exact start of day')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 23, 59, 59, 999)), 'day')).toBe(true, 'exact end of day')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 3, 0, 0, 0, 0)), 'day')).toBe(false, 'start of next day')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 1, 23, 59, 59, 999)), 'day')).toBe(true, 'end of previous day')
  expect(m.isSameOrAfter(m, 'day')).toBe(true, 'same moments are in the same day')
  expect(+m).toEqual(+mCopy, 'isSameOrAfter day should not change moment')
})

test('is same or after hour', () => {
  const m = dayjs(new Date(2011, 1, 2, 3, 4, 5, 6))
  const mCopy = dayjs(m)
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 3, 8, 9, 10)), 'hour')).toBe(true, 'hour match')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 3, 8, 9, 10)), 'hours')).toBe(true, 'plural should work')
  expect(m.isSameOrAfter(dayjs(new Date(2012, 1, 2, 3, 8, 9, 10)), 'hour')).toBe(false, 'year is later')
  expect(m.isSameOrAfter(dayjs(new Date(2010, 1, 2, 3, 8, 9, 10)), 'hour')).toBe(true, 'year is earlier')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 2, 2, 3, 8, 9, 10)), 'hour')).toBe(false, 'month is later')
  expect(m.isSameOrAfter(dayjs(new Date(2010, 12, 2, 3, 8, 9, 10)), 'hour')).toBe(true, 'month is earlier')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 3, 3, 8, 9, 10)), 'hour')).toBe(false, 'day is later')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 1, 3, 8, 9, 10)), 'hour')).toBe(true, 'day is earlier')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 4, 8, 9, 10)), 'hour')).toBe(false, 'hour is later')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 2, 8, 9, 10)), 'hour')).toBe(true, 'hour is earlier')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 3, 0, 0, 0)), 'hour')).toBe(true, 'exact start of hour')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 3, 59, 59, 999)), 'hour')).toBe(true, 'exact end of hour')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 4, 0, 0, 0)), 'hour')).toBe(false, 'start of next hour')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 2, 59, 59, 999)), 'hour')).toBe(true, 'end of previous hour')
  expect(m.isSameOrAfter(m, 'hour')).toBe(true, 'same moments are in the same hour')
  expect(+m).toEqual(+mCopy, 'isSameOrAfter hour should not change moment')
})

test('is same or after minute', () => {
  const m = dayjs(new Date(2011, 1, 2, 3, 4, 5, 6))
  const mCopy = dayjs(m)
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 3, 4, 9, 10)), 'minute')).toBe(true, 'minute match')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 3, 4, 9, 10)), 'minutes')).toBe(true, 'plural should work')
  expect(m.isSameOrAfter(dayjs(new Date(2012, 1, 2, 3, 4, 9, 10)), 'minute')).toBe(false, 'year is later')
  expect(m.isSameOrAfter(dayjs(new Date(2010, 1, 2, 3, 4, 9, 10)), 'minute')).toBe(true, 'year is earlier')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 2, 2, 3, 4, 9, 10)), 'minute')).toBe(false, 'month is later')
  expect(m.isSameOrAfter(dayjs(new Date(2010, 12, 2, 3, 4, 9, 10)), 'minute')).toBe(true, 'month is earlier')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 3, 3, 4, 9, 10)), 'minute')).toBe(false, 'day is later')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 1, 3, 4, 9, 10)), 'minute')).toBe(true, 'day is earlier')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 4, 4, 9, 10)), 'minute')).toBe(false, 'hour is later')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 2, 4, 9, 10)), 'minute')).toBe(true, 'hour is earlier')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 3, 5, 9, 10)), 'minute')).toBe(false, 'minute is later')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 3, 3, 9, 10)), 'minute')).toBe(true, 'minute is earlier')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 3, 4, 0, 0)), 'minute')).toBe(true, 'exact start of minute')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 3, 4, 59, 999)), 'minute')).toBe(true, 'exact end of minute')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 3, 5, 0, 0)), 'minute')).toBe(false, 'start of next minute')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 3, 3, 59, 999)), 'minute')).toBe(true, 'end of previous minute')
  expect(m.isSameOrAfter(m, 'minute')).toBe(true, 'same moments are in the same minute')
  expect(+m).toEqual(+mCopy, 'isSameOrAfter minute should not change moment')
})

test('is same or after second', () => {
  const m = dayjs(new Date(2011, 1, 2, 3, 4, 5, 6))
  const mCopy = dayjs(m)
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 3, 4, 5, 10)), 'second')).toBe(true, 'second match')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 3, 4, 5, 10)), 'seconds')).toBe(true, 'plural should work')
  expect(m.isSameOrAfter(dayjs(new Date(2012, 1, 2, 3, 4, 5, 10)), 'second')).toBe(false, 'year is later')
  expect(m.isSameOrAfter(dayjs(new Date(2010, 1, 2, 3, 4, 5, 10)), 'second')).toBe(true, 'year is earlier')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 2, 2, 3, 4, 5, 10)), 'second')).toBe(false, 'month is later')
  expect(m.isSameOrAfter(dayjs(new Date(2010, 12, 2, 3, 4, 5, 10)), 'second')).toBe(true, 'month is earlier')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 3, 3, 4, 5, 10)), 'second')).toBe(false, 'day is later')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 1, 3, 4, 5, 10)), 'second')).toBe(true, 'day is earlier')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 4, 4, 5, 10)), 'second')).toBe(false, 'hour is later')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 2, 4, 5, 10)), 'second')).toBe(true, 'hour is earlier')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 3, 5, 5, 10)), 'second')).toBe(false, 'minute is later')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 3, 3, 5, 10)), 'second')).toBe(true, 'minute is earlier')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 3, 4, 6, 10)), 'second')).toBe(false, 'second is later')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 3, 4, 4, 10)), 'second')).toBe(true, 'second is earlier')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 3, 4, 5, 0)), 'second')).toBe(true, 'exact start of second')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 3, 4, 5, 999)), 'second')).toBe(true, 'exact end of second')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 3, 4, 6, 0)), 'second')).toBe(false, 'start of next second')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 1, 2, 3, 4, 4, 999)), 'second')).toBe(true, 'end of previous second')
  expect(m.isSameOrAfter(m, 'second')).toBe(true, 'same moments are in the same second')
  expect(+m).toEqual(+mCopy, 'isSameOrAfter second should not change moment')
})

test('is same or after millisecond', () => {
  const m = dayjs(new Date(2011, 3, 2, 3, 4, 5, 10))
  const mCopy = dayjs(m)
  expect(m.isSameOrAfter(dayjs(new Date(2011, 3, 2, 3, 4, 5, 10)), 'millisecond')).toBe(true, 'millisecond match')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 3, 2, 3, 4, 5, 10)), 'milliseconds')).toBe(true, 'plural should work')
  expect(m.isSameOrAfter(dayjs(new Date(2012, 3, 2, 3, 4, 5, 10)), 'millisecond')).toBe(false, 'year is later')
  expect(m.isSameOrAfter(dayjs(new Date(2010, 3, 2, 3, 4, 5, 10)), 'millisecond')).toBe(true, 'year is earlier')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 4, 2, 3, 4, 5, 10)), 'millisecond')).toBe(false, 'month is later')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 2, 2, 3, 4, 5, 10)), 'millisecond')).toBe(true, 'month is earlier')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 3, 3, 3, 4, 5, 10)), 'millisecond')).toBe(false, 'day is later')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 3, 1, 1, 4, 5, 10)), 'millisecond')).toBe(true, 'day is earlier')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 3, 2, 4, 4, 5, 10)), 'millisecond')).toBe(false, 'hour is later')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 3, 1, 4, 1, 5, 10)), 'millisecond')).toBe(true, 'hour is earlier')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 3, 2, 3, 5, 5, 10)), 'millisecond')).toBe(false, 'minute is later')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 3, 2, 3, 3, 5, 10)), 'millisecond')).toBe(true, 'minute is earlier')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 3, 2, 3, 4, 6, 10)), 'millisecond')).toBe(false, 'second is later')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 3, 2, 3, 4, 4, 5)), 'millisecond')).toBe(true, 'second is earlier')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 3, 2, 3, 4, 6, 11)), 'millisecond')).toBe(false, 'millisecond is later')
  expect(m.isSameOrAfter(dayjs(new Date(2011, 3, 2, 3, 4, 4, 9)), 'millisecond')).toBe(true, 'millisecond is earlier')
  expect(m.isSameOrAfter(m, 'millisecond')).toBe(true, 'same moments are in the same millisecond')
  expect(+m).toEqual(+mCopy, 'isSameOrAfter millisecond should not change moment')
})

test('is same or after with invalid moments', () => {
  const m = dayjs()
  const invalid = dayjs(null)
  expect(invalid.isSameOrAfter(invalid)).toBe(false, 'invalid moments are not considered equal')
  expect(m.isSameOrAfter(invalid)).toBe(false, 'valid moment is not after invalid moment')
  expect(invalid.isSameOrAfter(m)).toBe(false, 'invalid moment is not after valid moment')
  expect(m.isSameOrAfter(invalid, 'year')).toBe(false, 'invalid moment year')
  expect(m.isSameOrAfter(invalid, 'month')).toBe(false, 'invalid moment month')
  expect(m.isSameOrAfter(invalid, 'day')).toBe(false, 'invalid moment day')
  expect(m.isSameOrAfter(invalid, 'hour')).toBe(false, 'invalid moment hour')
  expect(m.isSameOrAfter(invalid, 'minute')).toBe(false, 'invalid moment minute')
  expect(m.isSameOrAfter(invalid, 'second')).toBe(false, 'invalid moment second')
  expect(m.isSameOrAfter(invalid, 'milliseconds')).toBe(false, 'invalid moment milliseconds')
})