test: add vitest and svelte testing library (resolves #13)

package.json

@@ -10,6 +10,8 @@
 		"prepare": "husky",
 		"check": "svelte-kit sync && svelte-check --tsconfig ./tsconfig.json",
 		"check:watch": "svelte-kit sync && svelte-check --tsconfig ./tsconfig.json --watch",
+		"test": "vitest run",
+		"test:watch": "vitest",
 		"format": "prettier --write .",
 		"lint": "prettier --check . && eslint .",
 		"db:start": "docker compose up",
@@ -28,6 +30,8 @@
 		"@sveltejs/kit": "^2.49.0",
 		"@sveltejs/vite-plugin-svelte": "^6.2.1",
 		"@tailwindcss/vite": "^4.1.17",
+		"@testing-library/jest-dom": "^6.9.1",
+		"@testing-library/svelte": "^5.3.1",
 		"@tiptap/core": "3.7.2",
 		"@types/node": "^20.19.25",
 		"drizzle-kit": "^0.31.7",
@@ -39,6 +43,7 @@
 		"flowbite-svelte-icons": "^3.0.0",
 		"globals": "^16.5.0",
 		"husky": "^9.1.7",
+		"jsdom": "^29.0.1",
 		"lowlight": "^3.3.0",
 		"prettier": "^3.6.2",
 		"prettier-plugin-svelte": "^3.4.0",
@@ -47,7 +52,8 @@
 		"tailwindcss": "^4.1.17",
 		"typescript": "^5.9.3",
 		"typescript-eslint": "^8.47.0",
-		"vite": "^7.2.4"
+		"vite": "^7.2.4",
+		"vitest": "^4.1.2"
 	},
 	"dependencies": {
 		"@auth/drizzle-adapter": "^1.11.1",

src/lib/extractFormData.test.ts

@@ -0,0 +1,46 @@
+import { describe, it, expect } from 'vitest';
+import { extractFormData } from './extractFormData';
+import * as v from 'valibot';
+
+describe('extractFormData', () => {
+	it('should successfully extract and validate correct form data', async () => {
+		const formData = new FormData();
+		formData.append('name', 'John Doe');
+		formData.append('age', '30');
+
+		const request = new Request('http://localhost', {
+			method: 'POST',
+			body: formData
+		});
+
+		const schema = v.object({
+			name: v.string(),
+			age: v.string()
+		});
+
+		const result = await extractFormData(request, schema);
+
+		expect(result.error).toBeNull();
+		expect(result.data).toEqual({ name: 'John Doe', age: '30' });
+	});
+
+	it('should fail validation with missing required fields', async () => {
+		const formData = new FormData();
+		formData.append('age', '30');
+
+		const request = new Request('http://localhost', {
+			method: 'POST',
+			body: formData
+		});
+
+		const schema = v.object({
+			name: v.string(),
+			age: v.string()
+		});
+
+		const result = await extractFormData(request, schema);
+
+		expect(result.data).toBeUndefined();
+		expect(result.error).toBeTypeOf('string');
+	});
+});

vitest-setup.ts

@@ -0,0 +1 @@
+import '@testing-library/jest-dom/vitest';

vitest.config.ts

@@ -0,0 +1,12 @@
+import { defineConfig } from 'vitest/config';
+import { sveltekit } from '@sveltejs/kit/vite';
+import { svelteTesting } from '@testing-library/svelte/vite';
+
+export default defineConfig({
+	plugins: [sveltekit(), svelteTesting()],
+	test: {
+		include: ['src/**/*.{test,spec}.{js,ts}'],
+		environment: 'jsdom',
+		setupFiles: ['./vitest-setup.ts']
+	}
+});