Constructor mock not working in mocha unit test in Javascript

I am trying to raise an exception for an constructor method of EventHubBufferedProducerClient but its not working as expected. Am I missing something here.

My class method:

import { EventHubBufferedProducerClient } from '@azure/event-hubs';
import { logger } from '../logger';

this.producer = null;
async connect() {
   
    if (this.producer === null) {
      try {
        this.producer = new EventHubBufferedProducerClient(this.connStr, this.eHub);
      } catch (e) {
        logger.error(`Error while connecting to sEHub${this.eHub}`, e);
      }
    }
  }

Below is my test case:

//In before each
 sandbox = sinon.createSandbox();
 eventHubProducer = EventBusProducer('mockEventHubName', 'mockconnectionString');

 it('should log an error if connection fails', async () => {
      const logSpy = sandbox.spy(logger, 'error');
      
      // Force connection failure by throwing an error
      sandbox.stub(EventHubBufferedProducerClient.prototype, 'constructor').throws(new Error('Connection failed'));

      await eventHubProducer.connect();

      expect(eventHubProducer.producer).to.be.null;
      expect(logSpy.calledWith("Error while connecting to sEHub mockEventHubName")).to.be.true;
    });

I am getting below error:

should log an error if connection fails:
     AssertionError: expected EventHubBufferedProducerClient{ …(9) } to be null
      at Context.<anonymous> (EventBusProducer.test.js)
      at process.processTicksAndRejections (node:internal/process/task_queues:95:5)