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Testing isTomorrow Plugin Date Comparison in dayjs

This test suite validates the isTomorrow plugin functionality in the Day.js library, focusing on date comparison operations. The tests ensure accurate determination of whether a given date falls on the following day, utilizing mock date controls for consistent testing.

Test Coverage Overview

The test suite provides focused coverage of the isTomorrow plugin functionality:

Validates positive case with next day date
Tests negative case with non-consecutive dates
Handles date manipulation through dayjs().add()
Verifies plugin extension and integration

Implementation Analysis

The testing approach employs Jest’s testing framework with MockDate for controlled date handling. The implementation demonstrates clean test isolation through beforeEach and afterEach hooks, ensuring consistent date contexts for each test case.

Key patterns include plugin extension verification, date manipulation testing, and boolean assertion checks.

Technical Details

Testing Framework: Jest
Mocking Utility: MockDate
Plugin: isTomorrow
Setup: beforeEach/afterEach hooks
Assertion Methods: expect().toBeTruthy(), expect().toBeFalsy()

Best Practices Demonstrated

The test suite exemplifies several testing best practices including proper test isolation, mock date handling, and clear test case definition. Each test focuses on a specific functionality aspect with explicit assertions and clean setup/teardown procedures.

Isolated test environment
Controlled date manipulation
Clear assertion patterns
Proper plugin integration testing

iamkun/dayjs

test/plugin/isTomorrow.test.js

            
import MockDate from 'mockdate'
import dayjs from '../../src'
import isTomorrow from '../../src/plugin/isTomorrow'

dayjs.extend(isTomorrow)

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

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

it('is tomorrow', () => {
  expect(dayjs().add(1, 'day').isTomorrow()).toBeTruthy()
  expect(dayjs('2017-01-01').isTomorrow('2019-01-01', '2017-01-01')).toBeFalsy()
})