How to mock node readline?

Question

getUserInput calls a function when a user enters y in the CLI prompt:

export const getUserInput = (fn: () => void) => {
  const { stdin, stdout } = process;
  const rl = readline.createInterface({ input: stdin, output: stdout });
  rl.question("Can you confirm? Y/N", (answer: string) => {
    if (answer.toLowerCase() === "y") {
      fn();
    }
    rl.close();
  });
};

I need to create a test for getUserInput mocking Node's readline.

Currently I have tried the following but with no success, getting:

TypeError: rl.close is not a function

Is my mock implementation correct, and if not how can I fix it?

jest.mock("readline");
describe.only("program", () => {
    it.only("should execute a cb when user prompt in cli y", () => {
        const mock = jest.fn();
        getUserInput(mock);
        expect(mock).toHaveBeenCalled();
     });
 });

__mocks__/readline.ts (directory adjacent to node_module)

module.exports ={
  createInterface :jest.fn().mockReturnValue({
    question:jest.fn().mockImplementationOnce((_questionTest, cb)=> cb('y'))
  })
}

Answer 1

I was able to solve this issue by adding a mock the close function.

module.exports = {
  createInterface: jest.fn().mockReturnValue({
    question: jest.fn().mockImplementationOnce((_questionTest, cb) => cb("y")),
    close: jest.fn().mockImplementationOnce(() => undefined)
  })
};