test: add module enable/disable tests

- Add test cases to verify UTM tracking behavior when module is enabled
- Add test cases to verify UTM tracking is disabled when module is configured off
- Create new test fixture for disabled module configuration

This ensures the module's `enabled` configuration option works as expected.

test/fixtures/disabled/app.vue

@@ -0,0 +1,12 @@
+<template>
+  <div>
+    <h1>UTM Tracker</h1>
+    <pre>{{ $utm }}</pre>
+  </div>
+</template>
+
+<script setup>
+import { useNuxtApp } from "nuxt/app";
+
+const { $utm } = useNuxtApp();
+</script>

test/fixtures/disabled/nuxt.config.ts

@@ -0,0 +1,8 @@
+import UtmModule from "../../../src/module";
+
+export default defineNuxtConfig({
+  modules: [UtmModule],
+  utm: {
+    enabled: false,
+  },
+});

test/integration.test.ts

@@ -113,3 +113,40 @@ describe("ssr", async () => {
     });
   });
 });
+
+describe("Module configuration", () => {
+  describe("when enabled", async () => {
+    await setup({
+      rootDir: fileURLToPath(new URL("./fixtures/basic", import.meta.url)),
+      browser: true,
+    });
+
+    it("should track UTM parameters", async () => {
+      const page = await createPage(
+        "/?utm_source=test_source&utm_medium=test_medium"
+      );
+      const rawData = await page.evaluate(() =>
+        window.localStorage.getItem("nuxt-utm-data")
+      );
+      const entries = JSON.parse(rawData ?? "[]");
+      expect(entries.length).toBeGreaterThan(0);
+    });
+  });
+
+  describe("when disabled", async () => {
+    await setup({
+      rootDir: fileURLToPath(new URL("./fixtures/disabled", import.meta.url)),
+      browser: true,
+    });
+
+    it("should not track UTM parameters", async () => {
+      const page = await createPage(
+        "/?utm_source=test_source&utm_medium=test_medium"
+      );
+      const rawData = await page.evaluate(() =>
+        window.localStorage.getItem("nuxt-utm-data")
+      );
+      expect(rawData).toBeNull();
+    });
+  });
+});