test(mcp): await fetches in network tests to fix flake (#40553)

Author: yury-s

tests/mcp/network.spec.ts

@@ -67,15 +67,22 @@ test('browser_network_requests', async ({ client, server }) => {
 });
 
 test('browser_network_requests filter', async ({ client, server }) => {
-  server.setContent('/', `<script>
-    Promise.all([fetch('/api/users'), fetch('/api/orders'), fetch('/static/image.png')]);
-  </script>`, 'text/html');
+  server.setContent('/', '', 'text/html');
 
   await client.callTool({
     name: 'browser_navigate',
     arguments: { url: server.PREFIX },
   });
 
+  await client.callTool({
+    name: 'browser_evaluate',
+    arguments: {
+      function: `async () => {
+        await Promise.all([fetch('/api/users'), fetch('/api/orders'), fetch('/static/image.png')]);
+      }`,
+    },
+  });
+
   {
     const response = parseResponse(await client.callTool({
       name: 'browser_network_requests',
@@ -88,18 +95,23 @@ test('browser_network_requests filter', async ({ client, server }) => {
 });
 
 test('browser_network_requests numbers requests with stable indexes', async ({ client, server }) => {
-  server.setContent('/', `<script>
-    (async () => {
-      await fetch('/api/users');
-      await fetch('/api/orders');
-    })();
-  </script>`, 'text/html');
+  server.setContent('/', '', 'text/html');
 
   await client.callTool({
     name: 'browser_navigate',
     arguments: { url: server.PREFIX },
   });
 
+  await client.callTool({
+    name: 'browser_evaluate',
+    arguments: {
+      function: `async () => {
+        await fetch('/api/users');
+        await fetch('/api/orders');
+      }`,
+    },
+  });
+
   // Index assignment is stable across calls — the same request keeps the same number.
   const response = parseResponse(await client.callTool({
     name: 'browser_network_requests',