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Validating Weekday Plugin Implementation in iamkun/dayjs

This test suite validates the weekday plugin functionality in Day.js by comparing its behavior with Moment.js across different locales and first-day-of-week configurations. The tests ensure consistent date handling and locale-specific weekday calculations.

Test Coverage Overview

The test suite provides comprehensive coverage of the weekday plugin functionality across multiple locales (English, Chinese, Arabic).

Key areas tested include:

Basic weekday calculations and manipulations
Locale-specific first day of week handling
Negative and positive weekday index operations
Date format consistency with Moment.js

Implementation Analysis

The testing approach employs Jest’s unit testing framework with direct comparisons to Moment.js as the reference implementation.

Testing patterns include:

Mock date management for consistent testing environment
Locale switching between test cases
Direct API comparison with Moment.js methods
Value and format verification across different date manipulations

Technical Details

Testing infrastructure includes:

Jest as the testing framework
MockDate for date manipulation
Day.js with weekday plugin
Moment.js for comparison
Multiple locale configurations (en, zh-cn, ar)

Best Practices Demonstrated

The test suite exemplifies several testing best practices in JavaScript date handling.

Notable practices include:

Proper test isolation with beforeEach/afterEach hooks
Consistent state reset between tests
Comprehensive edge case coverage
Cross-library validation
Locale-aware testing methodology

iamkun/dayjs

test/plugin/weekday.test.js

            
import MockDate from 'mockdate'
import moment from 'moment'
import dayjs from '../../src'
import weekday from '../../src/plugin/weekday'
import '../../src/locale/zh-cn'
import '../../src/locale/ar'

dayjs.extend(weekday)

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

afterEach(() => {
  MockDate.reset()
  moment.locale('en')
  dayjs.locale('en')
})

it('Sunday is the first day of the week', () => {
  expect(dayjs().weekday()).toBe(moment().weekday())
  expect(dayjs().weekday(0).date()).toBe(moment().weekday(0).date())
  expect(dayjs().weekday(-7).format()).toBe(moment().weekday(-7).format())
  expect(dayjs().weekday(7).format()).toBe(moment().weekday(7).format())
})

it('Monday is the first day of the week', () => {
  moment.locale('zh-cn')
  dayjs.locale('zh-cn')
  expect(dayjs().weekday()).toBe(moment().weekday())
  expect(dayjs().weekday(0).date()).toBe(moment().weekday(0).date())
  expect(dayjs().weekday(-7).format()).toBe(moment().weekday(-7).format())
  expect(dayjs().weekday(7).format()).toBe(moment().weekday(7).format())
  const d1 = '2020-01-05'
  expect(dayjs(d1).weekday()).toBe(moment(d1).weekday())
  const d2 = '2020-01-07'
  expect(dayjs(d2).weekday()).toBe(moment(d2).weekday())
})

it('Saturday is the first day of the week', () => {
  moment.locale('ar')
  dayjs.locale('ar')
  expect(dayjs().weekday()).toBe(moment().weekday())
  expect(dayjs().weekday(0).date()).toBe(moment().weekday(0).date())
  expect(dayjs().weekday(-7).valueOf()).toBe(moment().weekday(-7).valueOf())
  expect(dayjs().weekday(7).valueOf()).toBe(moment().weekday(7).valueOf())
})