ViTest Mock is not replacing function

For some reason in ViTest mocks are not replacing my real function. I have a main function here

const { handler1 } = require(./path/handler1)

exports.mainFunction = async (event) => {
 try {
    const val1 = await handler1(event)
    console.log(val1)

Handler 1 looks like

exports.handler1 = async (data) => { return "real" }

I am trying to write unit tests for mainFunction where I can mock the response from handler1 (Handler1 already has its own unit tests)

import { handler1} from '../path/handler1.js';
vi.mock('../path/handler1.js');

describe('mainFunction()', function () {
  it("should return fake")  async function () {
    let handlerMock = {
      handler1: () => "Fake",
    };
    handler1.mockResolvedValue(handlerMock);
    await mainFunction("event")
    // mainFunction is outputting real and not fake

  }
}