vrandom/tests/pick.test.js

an easy way to work with random numbers in javascript

const pick = require('../lib/pick.js')

describe('pick', () => {
  it.each([
    { items: [1, 2, 3, 6, 5, 'hello', true, false], mockValue: 0.5, expected: 5 },
    { items: [1, 'bye', false, 45n], mockValue: 0.3124, expected: 'bye' },
    { items: [Infinity, 0, -Infinity], mockValue: 0.909309, expected: -Infinity },
    { items: ['my', NaN, 'is', 156, 'a', 'b', 'e', 25n, 't', 'g', 'AAAAA'], mockValue: 0.000152, expected: 'my' },
    { items: ['only'], mockValue: 0.01, expected: 'only' }
  ])("pick($items) should return '$expected' when Math.random returns $mockValue", ({ items, mockValue, expected }) => {
    jest.spyOn(Math, 'random').mockReturnValueOnce(mockValue)

    const actual = pick(items)
    expect(actual).toBe(expected)

    Math.random.mockRestore()
  })

  it('returns a random item from an array', () => {
    const arr = [1, 2, 3, 4, 5, 'hello', true, false]
    const actual = pick(arr)
    expect(arr.includes(actual)).toBeTruthy()
  })

  it('throws an error when called with not an array', () => {
    const str = 'Hello'
    function pickFromStr () {
      pick(str)
    }
    expect(pickFromStr).toThrowError(TypeError(`${str} is not an Array`))
  })
})