fix: support happy-dom environment

package.json

@@ -52,6 +52,7 @@
     "srvx": "^0.9.1"
   },
   "devDependencies": {
+    "@happy-dom/global-registrator": "^20.0.8",
     "@mitata/counters": "^0.0.8",
     "@types/connect": "^3.4.38",
     "@types/express": "^5.0.4",
@@ -72,6 +73,7 @@
     "fetchdts": "^0.1.7",
     "get-port-please": "^3.2.0",
     "h3-nightly": "3.0.0-20251023-133803-7632fc3",
+    "happy-dom": "^20.0.8",
     "hono": "^4.10.3",
     "memoirist": "^0.4.0",
     "mitata": "^1.0.34",

src/response.ts

@@ -154,19 +154,14 @@ function mergeHeaders(
   return target;
 }
 
-const ERROR_FROZEN = () => {
+const frozenHeaders = () => {
   throw new Error("Headers are frozen");
 };
 
 class FrozenHeaders extends Headers {
-  override set(): void {
-    ERROR_FROZEN();
-  }
-  override append(): void {
-    ERROR_FROZEN();
-  }
-  override delete(): void {
-    ERROR_FROZEN();
+  constructor(init?: HeadersInit) {
+    super(init);
+    this.set = this.append = this.delete = frozenHeaders;
   }
 }
 

test/happydom.test.ts

@@ -0,0 +1,45 @@
+import { afterAll, beforeAll, describe, expect, test } from "vitest";
+import { GlobalRegistrator } from "@happy-dom/global-registrator";
+
+describe("happydom", () => {
+  // Lazy import after setting up globals to apply happydom polyfills
+  let h3: typeof import("../src/index.ts");
+
+  beforeAll(async () => {
+    await GlobalRegistrator.register({
+      url: "http://localhost:3000",
+      width: 1920,
+      height: 1080,
+    });
+  });
+
+  afterAll(async () => {
+    await GlobalRegistrator.unregister();
+  });
+
+  test("import h3", async () => {
+    h3 = await import("../src/index.ts");
+  });
+
+  test("render works", async () => {
+    const app = new h3.H3();
+    app.post("/", async (event) => {
+      return new Response(event.req.body, {
+        headers: event.req.headers,
+      });
+    });
+
+    const req = new Request("http://localhost:3000/", {
+      method: "POST",
+      body: JSON.stringify({ hello: "world" }),
+      headers: {
+        "Content-Type": "application/json",
+      },
+    });
+    const res = await app.fetch(req);
+    expect(res.status).toBe(200);
+    expect(res.headers.get("Content-Type")).toBe("application/json");
+    const json = await res.json();
+    expect(json).toEqual({ hello: "world" });
+  });
+});