Add endpoint and tests for withMonitor error handling to cover issue:16749

Introduce a new endpoint `/crash-in-with-monitor/:id` that demonstrates error handling using Sentry's `withMonitor` API. Added tests to ensure the app gracefully handles exceptions and validates consistent PID behavior during monitoring.

Author: cod1k

dev-packages/e2e-tests/test-applications/node-express/src/app.ts

@@ -29,6 +29,18 @@ const port = 3030;
 
 app.use(mcpRouter);
 
+app.get('/crash-in-with-monitor/:id', async (req, res) => {
+  try {
+    await Sentry.withMonitor('express-crash', async () => {
+      throw new Error(`This is an exception withMonitor: ${req.params.id}`);
+    });
+    res.sendStatus(200);
+  } catch (error: any) {
+    res.status(500);
+    res.send({ message: error.message, pid: process.pid });
+  }
+});
+
 app.get('/test-success', function (req, res) {
   res.send({ version: 'v1' });
 });

dev-packages/e2e-tests/test-applications/node-express/tests/errors.test.ts

@@ -40,3 +40,14 @@ test('Should record caught exceptions with local variable', async ({ baseURL })
   const frames = errorEvent.exception?.values?.[0]?.stacktrace?.frames;
   expect(frames?.[frames.length - 1]?.vars?.randomVariableToRecord).toBeDefined();
 });
+
+test('To not crush app from withMonitor', async ({ baseURL }) => {
+  const doRequest = async (id: number) => {
+    const response = await fetch(`${baseURL}/crash-in-with-monitor/${id}`)
+    return response.json();
+  }
+  const [response1, response2] = await Promise.all([doRequest(1), doRequest(2)])
+  expect(response1.message).toBe('This is an exception withMonitor: 1')
+  expect(response2.message).toBe('This is an exception withMonitor: 2')
+  expect(response1.pid).toBe(response2.pid) //Just to double-check, TBS
+});