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Testing Developer Helper Warning System in Day.js

This test suite validates the developer helper functionality in Day.js, focusing on warning messages for common usage mistakes. It ensures proper error handling and user guidance for timestamp parsing, locale settings, and date format parsing.

Test Coverage Overview

The test suite comprehensively covers various developer warning scenarios in Day.js:

Year parsing as Unix timestamp warnings
Unix timestamp string format validation
Custom parse format plugin requirements
Locale loading sequence verification

Each test case validates specific warning messages and their triggers.

Implementation Analysis

The testing approach utilizes Jest’s mocking capabilities to intercept and verify console warnings. The implementation employs spy functions to monitor console output and validates exact warning message content. The tests follow AAA (Arrange-Act-Assert) pattern with clear setup and verification steps.

Technical Details

Testing tools and setup include:

Jest test framework for assertions and mocking
MockDate for date manipulation
Console spy functionality for warning interception
Global mock functions for console warnings
Before/after hooks for test environment management

Best Practices Demonstrated

The test suite exemplifies several testing best practices:

Isolated test cases with clear purpose
Proper test environment cleanup
Mock management for external dependencies
Specific assertion messages
Consistent test structure across cases

iamkun/dayjs

test/plugin/devHelper.test.js

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

dayjs.extend(devHelper)

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

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

global.console.warn = jest.genMockFunction()


it('Warning: passing Year as a Number will be parsed as a Unix timestamp', () => {
  const consoleSpy = jest.spyOn(console, 'warn')
  dayjs(2020)
  expect(consoleSpy).toHaveBeenCalledWith('Guessing you may want to parse the Year 2020, you should pass it as a String 2020, not a Number. Otherwise, 2020 will be treated as a Unix timestamp')
})

it('Warning Passing Unix timestamp as a String not Number', () => {
  const consoleSpy = jest.spyOn(console, 'warn')
  dayjs('1231231231231')
  expect(consoleSpy).toHaveBeenCalledWith('To parse a Unix timestamp like 1231231231231, you should pass it as a Number. https://day.js.org/docs/en/parse/unix-timestamp-milliseconds')
})

it('Warning Enable customParseFormat plugin while passing the second format parameter', () => {
  const consoleSpy = jest.spyOn(console, 'warn')
  dayjs('2020', 'YYYY')
  expect(consoleSpy).toHaveBeenCalledWith('To parse a date-time string like 2020 using the given format, you should enable customParseFormat plugin first. https://day.js.org/docs/en/parse/string-format')
})

it('Warning: Setting locale before loading locale', () => {
  const consoleSpy = jest.spyOn(console, 'warn')
  dayjs.locale('zh-cn')
  expect(consoleSpy).toHaveBeenCalledWith('Guessing you may want to use locale zh-cn, you have to load it before using it. https://day.js.org/docs/en/i18n/loading-into-nodejs')
})