Add unit tests for 67% coverage #11

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: a6b8

jest.config.mjs

@@ -2,5 +2,11 @@ export default {
     transform: {},
     testMatch: [
         '**/tests/**/*.test.mjs'
+    ],
+    testTimeout: 15000,
+    maxWorkers: 1,
+    coveragePathIgnorePatterns: [
+        '/node_modules/',
+        'src/index.mjs'
     ]
 }