vrandom/tests/lowercaseLetter.test.js

an easy way to work with random numbers in javascript

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

describe('lowercase letter', () => {
  it('should return a random lowercase letter', () => {
    const lowerAlphabet = 'abcdefghijklmnopqrstuvwxyz'
    const letter = lowercaseLetter()

    expect(lowerAlphabet.includes(letter)).toBe(true)
  })

  it.each([
    { mockValue: 0.03842307692307692, expected: 'a' },
    { mockValue: 0.07684615384615384, expected: 'b' },
    { mockValue: 0.11526923076923076, expected: 'c' },
    { mockValue: 0.15369230769230768, expected: 'd' },
    { mockValue: 0.1921153846153846, expected: 'e' },
    { mockValue: 0.2305384615384615, expected: 'f' },
    { mockValue: 0.2689615384615385, expected: 'g' },
    { mockValue: 0.30738461538461537, expected: 'h' },
    { mockValue: 0.34580769230769226, expected: 'i' },
    { mockValue: 0.3842307692307692, expected: 'j' },
    { mockValue: 0.42265384615384616, expected: 'k' },
    { mockValue: 0.46107692307692305, expected: 'l' },
    { mockValue: 0.49949999999999994, expected: 'm' },
    { mockValue: 0.537923076923077, expected: 'n' },
    { mockValue: 0.5763461538461538, expected: 'o' },
    { mockValue: 0.6147692307692307, expected: 'p' },
    { mockValue: 0.6531923076923076, expected: 'q' },
    { mockValue: 0.6916153846153845, expected: 'r' },
    { mockValue: 0.7300384615384615, expected: 's' },
    { mockValue: 0.7684615384615384, expected: 't' },
    { mockValue: 0.8068846153846153, expected: 'u' },
    { mockValue: 0.8453076923076923, expected: 'v' },
    { mockValue: 0.8837307692307692, expected: 'w' },
    { mockValue: 0.9221538461538461, expected: 'x' },
    { mockValue: 0.960576923076923, expected: 'y' },
    { mockValue: 0.9989999999999999, expected: 'z' }
  ])("lowercaseLetter() should return '$expected` when Math.random() returns $mockValue", ({ mockValue, expected }) => {
    jest.spyOn(Math, 'random').mockReturnValueOnce(mockValue)

    const actual = lowercaseLetter()

    expect(actual).toBe(expected)

    Math.random.mockRestore()
  })

  it('returns a string', () => {
    const actual = lowercaseLetter()

    expect(typeof actual).toBe('string')
  })

  it('returns a string of length 1', () => {
    const actual = lowercaseLetter()

    expect(actual.length).toBe(1)
  })
})