I have a function that store data into database:

async function save(id, fields) {
  ...
  const exist = await knex('table').select('..').where({ id });

  if (exist) {
     await knex('table').update([...fields...]).where({ id });
  } else {
     await knex('table').insert([...fields...]);
  }
  ....
}

How I test this function? I searched in knex docs but got no answer there.

What are the best practices?

Should I connect to "test" database and execute the database? but I think in this case I'll need to update the schema and the data which is kind annoying.

Should I create transaction every time I change the database and undo after the test complete?

Maybe mock knex? but how I know if the type and the query is correct?

Something else?