@jeremyckahn/farmhand/src/common/services/randomNumber.test.js

A farming game

import { randomNumberService } from './randomNumber.js'

const chance = 0.6

describe('RandomNumberService', () => {
  describe('isRandomNumberLessThan', () => {
    test('it returns true when random number is below chance', () => {
      vitest
        .spyOn(randomNumberService, 'generateRandomNumber')
        .mockReturnValueOnce(chance - 0.01)

      expect(randomNumberService.isRandomNumberLessThan(chance)).toEqual(true)
    })

    test('it returns true when random number is same as chance', () => {
      vitest
        .spyOn(randomNumberService, 'generateRandomNumber')
        .mockReturnValueOnce(chance)

      expect(randomNumberService.isRandomNumberLessThan(chance)).toEqual(true)
    })

    test('it returns false when random number is above chance', () => {
      vitest
        .spyOn(randomNumberService, 'generateRandomNumber')
        .mockReturnValueOnce(chance + 0.01)

      expect(randomNumberService.isRandomNumberLessThan(chance)).toEqual(false)
    })
  })
})