test: add vitest & initial tests

package.json

@@ -27,6 +27,7 @@
   "scripts": {
     "preinstall": "npx only-allow pnpm",
     "start": "npx simple-server .",
+    "test": "vitest",
     "demo": "npx simple-server .",
     "site": "pnpm --filter site start",
     "build": "pnpm run clean && tsc && pnpm run copy:source",
@@ -60,7 +61,8 @@
     "husky": "^9.1.6",
     "prettier": "^3.3.3",
     "size-limit": "^11.1.6",
-    "typescript": "^5.6.3"
+    "typescript": "^5.6.3",
+    "vitest": "^2.1.4"
   },
   "size-limit": [
     {

src/utils/serialize.mjs

@@ -3,7 +3,6 @@ export function serialize(value) {
     case "number":
     case "boolean":
     case "object":
-    case "undefined":
       return JSON.stringify(value);
     default:
       return value;

test/serialize.test.ts

@@ -0,0 +1,27 @@
+import { describe, expect, test } from "vitest";
+import { serialize } from "../src/utils/serialize.mjs";
+
+describe("serialize", () => {
+  test("should stringify number", () => {
+    const result = serialize(3);
+    expect(result).toBeTypeOf("string");
+    expect(result).toEqual("3");
+  });
+
+  test("should stringify boolean", () => {
+    const result = serialize(false);
+    expect(result).toBeTypeOf("string");
+    expect(result).toEqual("false");
+  });
+
+  test("should stringify object", () => {
+    const result = serialize({ hello: "world" });
+    expect(result).toBeTypeOf("string");
+    expect(result).toEqual('{"hello":"world"}');
+  });
+
+  test("should return undefined", () => {
+    const result = serialize(undefined);
+    expect(result).toBeUndefined();
+  });
+});