diff --git a/deno.json b/deno.json
index 369b08670..279f0df69 100644
--- a/deno.json
+++ b/deno.json
@@ -129,7 +129,8 @@
       "./packages"
     ],
     "exclude": [
-      "./packages/init/src/templates/**"
+      "./packages/init/src/templates/**",
+      "./packages/next/**"
     ]
   }
 }
diff --git a/mise.toml b/mise.toml
index fa64e5194..b2c940411 100644
--- a/mise.toml
+++ b/mise.toml
@@ -304,12 +304,18 @@ shell = "nu -c"
 run = '''
 let pkgs = ($env.usage_packages | split row " " | where ($it | is-not-empty))
 mise run prepare-each ...$pkgs
-mise run check-each ...$pkgs
 for pkg in $pkgs {
-  print $"Running tests for package: ($pkg)"
-  deno task --filter $"@fedify/($pkg)" test
-  pnpm --filter $"@fedify/($pkg)" test
-  pnpm --filter $"@fedify/($pkg)" test:bun
+  if ($"packages/($pkg)/deno.json" | path exists) {
+    mise run check-each $pkg
+    print $"Running Deno tests for package: ($pkg)"
+    deno task --filter $"@fedify/($pkg)" test
+  }
+  if ($"packages/($pkg)/package.json" | path exists) {
+    print $"Running Node.js tests for package: ($pkg)"
+    pnpm --filter $"@fedify/($pkg)" test
+    print $"Running Bun tests for package: ($pkg)"
+    pnpm --filter $"@fedify/($pkg)" test:bun
+  }
 }
 '''
 
diff --git a/packages/next/package.json b/packages/next/package.json
index 2401b777c..4e79edadb 100644
--- a/packages/next/package.json
+++ b/packages/next/package.json
@@ -58,6 +58,8 @@
     "build:self": "tsdown",
     "build": "pnpm --filter @fedify/next... run build:self",
     "prepack": "pnpm build",
-    "prepublish": "pnpm build"
+    "prepublish": "pnpm build",
+    "test": "node --test dist/",
+    "test:bun": "bun test"
   }
 }
diff --git a/packages/next/src/index.test.ts b/packages/next/src/index.test.ts
new file mode 100644
index 000000000..430d32da2
--- /dev/null
+++ b/packages/next/src/index.test.ts
@@ -0,0 +1,115 @@
+import {
+  createFederation,
+  InProcessMessageQueue,
+  MemoryKvStore,
+} from "@fedify/fedify";
+import { test } from "@fedify/fixture";
+import { strict as assert } from "node:assert";
+import {
+  fedifyWith,
+  integrateFederation,
+  isFederationRequest,
+  isNodeInfoRequest,
+} from "./index.ts";
+
+test("Accept header detection", () => {
+  const request = new Request("https://example.com/", {
+    headers: {
+      Accept: "application/activity+json",
+    },
+  });
+
+  assert.strictEqual(isFederationRequest(request), true);
+});
+
+test("Content-Type header detection", () => {
+  const request = new Request("https://example.com/", {
+    method: "POST",
+    headers: {
+      "Content-Type": "application/activity+json",
+    },
+  });
+
+  assert.strictEqual(isFederationRequest(request), true);
+});
+
+test("NodeInfo route detection", () => {
+  const request1 = new Request("https://example.com/.well-known/nodeinfo", {});
+
+  const request2 = new Request(
+    "https://example.com/.well-known/x-nodeinfo2",
+    {},
+  );
+
+  assert.strictEqual(isNodeInfoRequest(request1), true);
+  assert.strictEqual(isNodeInfoRequest(request2), true);
+});
+
+test("Non-federation request delegation", async () => {
+  const federation = createFederation({
+    kv: new MemoryKvStore(),
+    queue: new InProcessMessageQueue(),
+  });
+  const customMiddleware = (request: Request) => {
+    if (request.url === "https://example.com/test") {
+      return new Response("Custom middleware response");
+    }
+    return new Response("Default response");
+  };
+  const middleware = fedifyWith(federation)(customMiddleware);
+
+  const request = new Request("https://example.com/", {
+    headers: {
+      Accept: "text/html",
+    },
+  });
+
+  const request2 = new Request("https://example.com/test", {
+    headers: {
+      Accept: "text/html",
+    },
+  });
+
+  assert.strictEqual(isFederationRequest(request), false);
+  assert.strictEqual(isFederationRequest(request2), false);
+
+  const response1 = await middleware(request);
+  const response2 = await middleware(request2);
+
+  assert.strictEqual(await response1.text(), "Default response");
+  assert.strictEqual(await response2.text(), "Custom middleware response");
+});
+
+test("Custom not-found/not acceptable handler", async () => {
+  const federation = createFederation({
+    kv: new MemoryKvStore(),
+    queue: new InProcessMessageQueue(),
+  });
+
+  // Set up a dispatcher that always returns null to simulate a not acceptable scenario
+  federation.setActorDispatcher("/users/{identifier}", () => null);
+
+  const handler = integrateFederation(federation, undefined, {
+    onNotFound: () => new Response("Custom not found", { status: 418 }),
+    onNotAcceptable: () =>
+      new Response("Custom not acceptable", { status: 418 }),
+  });
+
+  const response1 = await handler(
+    new Request("https://example.com/missing", {
+      headers: { Accept: "application/activity+json" },
+    }),
+  );
+
+  assert.strictEqual(response1.status, 418);
+  assert.strictEqual(await response1.text(), "Custom not found");
+
+  const response2 = await handler(
+    new Request("https://example.com/users/123", {
+      headers: { Accept: "text/html" },
+    }),
+  );
+
+  assert.strictEqual(response2.status, 418);
+  assert.strictEqual(await response2.text(), "Custom not acceptable");
+});