Add tests that will fail with ECMA 6 parsing

src/fixtures/nuxt/async.expected.js

@@ -0,0 +1,18 @@
+const getAllDynamicRoute = async function() {
+    const routes = await (async () => {
+      return ['/posts/hello-world', '/posts/hello-again'];
+    })();
+    return routes;
+  };
+  
+  export default {
+    target: 'static',
+    router: {base: '/docs/'},
+    mode: 'universal',
+    generate: {
+      async routes () {
+        return getAllDynamicRoute();
+      }
+    }
+  };
+  

src/fixtures/nuxt/async.js

@@ -0,0 +1,15 @@
+const getAllDynamicRoute = async function() {
+  const routes = await (async () => {
+    return ['/posts/hello-world', '/posts/hello-again'];
+  })();
+  return routes;
+};
+
+export default {
+  mode: 'universal',
+  generate: {
+    async routes () {
+      return getAllDynamicRoute();
+    }
+  }
+};