Properly setup mocking for pg-promose in express.js for supertests

I am using pg-promose inside its own module to initialise a connection to DB and then use that connection in my route modules or anywhere else its imported.

import pgPromise from 'pg-promise'

let psqlClient
const pgp = pgPromise({/* Initialization Options */ })
const connection = {
    connectionString: process.env.PSQL_URI || "postgres://postgres@postgresql:5432",
    max: process.env.PSQL_POOL_SIZE || 15
}
export const connectPSQL = async () => {
    try {
        psqlClient = pgp(connection);
    } catch (e) {
        console.error(`Error Connecting to DB: ${e}`);
    }
}


export const getPSQLClient = () => {
    return psqlClient;
};

export const getURL = () => {
    return process.env.PSQL_URI
}

This is a pretty simple module however I cannot seem to wrap my head around on how to mock it in a unit test for a specific route. Following guides like this one I am doing something simple like:

import request from 'supertest';
import express from 'express';
import { getPSQLClient } from "../clients/postgresql.js";
import {get as GETFoo} from '../routes/v1/foo/index.js';
import { jest } from '@jest/globals';

jest.mock("../clients/postgresql.js")

const app = express();

app.use(express.json());
app.use('/v1/foo/index.js', GETFoo);


describe('Sample Test', () => {
    it('should test that true === true', () => {
      expect(getPSQLClient).toHaveBeenCalledTimes(1);
    })
  })

But this is returning: Matcher error: received value must be a mock or spy function which seems like the mocking is not being done correctly.

What I ultimately want is to be able to mock query results since my route involves querying like:

 let result = await psqlClient.any(
            "SELECT * FROM goo WHERE id=$1 LIMIT 1",
            [req.params.rid]
        )

I just want to plug in my own mocked result