How to mock SQL Server database connection using jest - sql-server

Question

I want to mock a SQL Server connection.
Here is the code to be tested:
import sql from 'mssql';
export class DBConnection {
public async query(input: any): Promise<any> {
const config = {
server: "server",
port: 1234,
database: "db",
user: "user",
password: "password",
trustServerCertificate: true
};
try {
const pool = new sql.ConnectionPool(config);
await pool.connect();
let request = pool.request();
request.input('key', sql.VarChar, input.key);
request.input('value', sql.VarChar, input.value);
let insertQuery = "INSERT INTO SOMETABLE (key, value) OUTPUT INSERTED.key VALUES (#key, #value)"
return await request.query(insertQuery);
} catch (err) {
console.error(err);
}
}
}
My question is: how to create mock of sql.ConnectionPool? I tried using jest.Mocked to mock entire module, tried using jest.spy to mock the constructor or specific method, but seems none of them working
Here is the mock test, apparently not working
import { DBConnection } from './db';
import sql from 'mssql';
jest.mock('mssql');
const mockpool = sql as jest.Mocked<typeof sql>;
const pool = mockpool.ConnectionPool;
let db = new DBConnection();
describe('DB test', () => {
beforeEach(() => {
jest.spyOn(sql.ConnectionPool.prototype, 'connect').mockImplementation(() => pool);
});
afterEach(() => {
jest.resetAllMocks();
});
it('should have success response', async () => {
const input = { key: 'key1', value: 1234 }
try {
const response = await db.query(input);
expect(response).toBe("key1");
} catch (e) {
}
});
});