Add Jest Testing

[maxsu]

1. Add a testing script: "test": "jest" 🤡

2. Add html testing: *@testing-library/jest-domt ref: dom testing guide

3. Add preact testing: @testing-library/preact ref: preact component testing guide

4. Add typescript tests: ts-jest

5. Use a typescript jest.config file: ts-node

6. Add jest.config.ts:

   • root: The project's import root is /src
   • transform: Translate .ts/.tsx tests using ts-jest
   • testRegex: Tests files are
     1. Any .ts/.tsx file in /src/__tests__/ (for example: /src/__tests__/index.ts, /src/__tests__/example.test.ts)
     2. Any file named /src/**/*.test.[ts,tsx]
     3. Any file named /src/**/*.spec.[ts,tsx]
     4. Any file named /src/**/test.[ts,tsx]
     5. Any file named /src/**/spec.[ts,tsx]
   • moduleFileExtensions: Jest tests may import ts, tsx, js, jsx, mjs, and json modules, and also node binary modules.
   • setupFilesAfterEnv: install jest-dom for each test module

7. Added /srt/__tests__/example.test.ts

To run tests, perform npm test.

Breaking Changes: None.