add unit tests

vite.config.ts

@@ -1,4 +1,4 @@
-import { defineConfig } from 'vite';
+import { defineConfig } from 'vitest/config';
 import react from '@vitejs/plugin-react';
 import { resolve } from 'node:path';
 
@@ -15,4 +15,18 @@ export default defineConfig({
             external: ['react'],
         },
     },
+    test: {
+        environment: 'jsdom',
+        setupFiles: ['./tests/setup.ts'],
+        coverage: {
+            provider: 'v8',
+            include: ['src/**/*.{ts,tsx}'],
+            exclude: ['src/index.ts'],
+            thresholds: {
+                lines: 95,
+                functions: 95,
+                branches: 90,
+            },
+        },
+    },
 });