how to mock a module that takes a parameter - node.js

Question

I am trying to write a unit test for code that uses pg-promise, it looks like this:
const pgp = require('pg-promise')();
const cn = {
host: process.env.DB_HOST,
port: 5432,
database: process.env.DB_NAME,
user: process.env.DB_USER,
password: process.env.DB_PASSWORD
};
function insertStuff(stuff) {
let db = pgp(cn);
return db.one('INSERT INTO test(stuff) VALUES ($1) RETURNING id, stuff', [stuff])
.then(data => {
return data
})
}
module.exports.insertStuff = insertStuff
The test code looks like this:
const mockFakeDb = {
one: jest.fn()
}
jest.mock("pg-promise", () => {
return mockFakeDb
})
const insertStuff = require("../src/db-utils").insertStuff
test("params for inserting stuff are correct", done => {
mockFakeDb.one.mockImplementationOnce(() => {
return Promise.resolve({id: 123456789, stuff: "stuff"})
insertStuff("stuff").then((data) => {
const insertCall = fakeDb.one.mock.calls[0]
expect(insertCall).toHaveBeenCalledTimes(1)
done()
})
})
so in trying to mock pg-promise require I get an error:
TypeError: require(...) is not a function.
I can see that pg-promise has a function which takes parameters (the second brackets) but not sure how to now mock this?

Answer 1

For anybody else not quite sure how to do this:
const fakeDB = {
one: jest.fn()
}
function fakePgpFunc() {
return fakeDB
}
fakePgpFunc.end = jest.fn()
jest.doMock("pg-promise", () => {
return jest.fn(() => fakePgpFunc)
})
const insertStuff = require("../src/db-utils").insertStuff
beforeEach(() => {
jest.clearAllMocks()
})
test("params for inserting stuff are correct", done => {
fakeDB.one.mockImplementationOnce(() => {
return Promise.resolve({"stuff": "Stuff", "id": 123456789})
})
insertStuff("Stuff").then((data) => {
expect(fakeDB.one).toHaveBeenCalledTimes(1)
const insertStuffCall = fakeDB.one.mock.calls[0]
expect(insertStuffCall[0]).toEqual("INSERT INTO test(stuff) VALUES ($1) RETURNING id, stuff")
expect(queryInsertCall[1]).toEqual(["Stuff"])
expect(data).toEqual({id: 123456789, stuff: "Stuff"})
expect(fakePgpFunc.end).toHaveBeenCalledTimes(1)
done()
})
})