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Validating TypeScript Declaration Files in dayjs

This test suite validates the TypeScript declarations for Day.js plugins, ensuring proper type definition files exist for each plugin in the codebase. It performs automated verification of plugin type declarations to maintain TypeScript compatibility and type safety.

Test Coverage Overview

The test provides comprehensive coverage of plugin type declarations by scanning the plugin directory and verifying corresponding .d.ts files.

Validates existence of TypeScript declaration files for all plugins
Ensures 1:1 mapping between plugin implementations and type definitions
Covers file system integration for plugin discovery
Handles path resolution across different environments

Implementation Analysis

The testing approach utilizes Jest’s file system capabilities to perform systematic validation of plugin declarations. The implementation employs fs.readdirSync for directory scanning and path.join for cross-platform path handling, ensuring reliable plugin type verification across different environments.

Synchronous file system operations for deterministic testing
Path normalization for cross-platform compatibility
Directory traversal pattern for plugin discovery

Technical Details

Testing Framework: Jest
Node.js Modules: fs, path
Directory Structure: src/plugin for implementations, types/plugin for declarations
File Pattern: .d.ts suffix for type declarations
Testing Environment: Node.js runtime

Best Practices Demonstrated

The test suite exemplifies robust validation practices for TypeScript integration in JavaScript projects. It demonstrates automated type declaration verification, ensuring maintainability and type safety.

Automated type declaration validation
Consistent file naming conventions
Structured project organization
Cross-platform compatibility considerations

iamkun/dayjs

test/plugin/declarations.test.js

            
import fs from 'fs'
import path from 'path'

const pluginDir = '../../src/plugin'
const pluginTypeDir = '../../types/plugin'

it('Plugin declarations', () => {
  fs.readdirSync(path.join(__dirname, pluginDir))
    .forEach((l) => {
      expect(fs.existsSync(path.join(__dirname, pluginTypeDir, `${l}.d.ts`)))
        .toBe(true)
    })
})