test.js

const { randomJoke, randomTen, jokeById } = require('./handler');

console.log('randomJoke', randomJoke());
console.log('randomTen', randomTen());

it('should render the joke with an id of 1', () => {
    expect(jokeById(1)).toEqual(
        {
            "id": 1,
            "type": "general",
            "setup": "What did the fish say when it hit the wall?",
            "punchline": "Dam."
        }
    );
});

it('should return undefined with an invalid id', () => {
    expect(jokeById('one')).toEqual(undefined);
    expect(jokeById('1')).toEqual(undefined);
    expect(jokeById()).toEqual(undefined);
});