Add Vitest testing infrastructure with simple utility tests

[Copilot]

Overview

This PR adds a basic testing infrastructure to the project using Vitest, enabling unit testing for TypeScript/JavaScript code.

Changes

Testing Infrastructure

• Installed dependencies: Added vitest, @vitest/ui, jsdom, and happy-dom as dev dependencies
• Created vitest.config.ts: Configured Vitest to use happy-dom environment with global test APIs
• Added test scripts to package.json:
  • npm run test - Run tests in watch mode
  • npm run test:run - Run tests once
  • npm run test:ui - Run tests with interactive UI

Test Files

• Created src/lib/utils.ts: Extracted the generateRandomString function into a reusable utility module with proper TypeScript typing and documentation
• Created src/lib/utils.test.ts: Added 4 comprehensive tests covering:
  • String length validation
  • Alphanumeric character validation
  • Edge case handling (zero length)
  • Randomness verification

Documentation

• Updated readme.md: Added a "Testing" section with instructions on how to run tests and information about test file naming conventions

Test Results

All tests are passing:

✓ src/lib/utils.test.ts (4 tests) 4ms
  Test Files  1 passed (1)
       Tests  4 passed (4)

Security

No security vulnerabilities were introduced. CodeQL analysis returned 0 alerts.

Future Work

This testing infrastructure can now be easily extended to add tests for:

• Svelte components (with @testing-library/svelte)
• Additional utility functions
• Graph manipulation logic
• Edge cases in the visualization layer

Original prompt

plan and create a very simple test using vitest for this project.

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[ramadhanafif]

This is not enough, try to do the testing if certain words appear in the webpage. For example, the "ForSyDe" should be exist. @copilot

[ramadhanafif]

This is not enough, try to do the testing if certain words appear in the webpage. For example, the "ForSyDe" should be exist. @copilot