Testing: Set up test infrastructure and mocks

[fegge]

Parent issue: #90

Overview

Set up the foundational test infrastructure before writing individual tests.

Tasks

• Add devDependencies: jsdom, nyc, @vscode/test-electron
• Create directory structure:

  test/
  ├── unit/
  ├── extension/
  ├── webview/
  ├── mocks/
  └── fixtures/
  

• Create test/mocks/vscode.ts with factories:
  • createMockWorkspaceFolder(path)
  • createMockTextEditor(uri, selection?)
  • createMockExtensionContext()
• Create test/fixtures/ with sample .weaudit files (valid, corrupt, empty, legacy)
• Add npm scripts to package.json:

  "test": "npm run test:unit && npm run test:ext",
  "test:unit": "mocha -r ts-node/register test/unit/**/*.test.ts",
  "test:ext": "vscode-test",
  "coverage": "nyc npm run test:unit"

• Configure nyc coverage thresholds (80% types.ts, 60% overall)

Acceptance Criteria

• npm run test:unit executes successfully
• Mock factories importable in tests
• Fixtures available for subsequent test issues

Reference

See TESTING.md