tabler/shared/lib/pseudo-random.test.ts

import { describe, expect, it } from 'vitest'
import { randomDate, randomItem, randomNumber, timeagoLabel } from './pseudo-random'

describe('randomNumber', () => {
  it('is deterministic for a given index', () => {
    expect(randomNumber(5, 0, 100)).toBe(randomNumber(5, 0, 100))
  })

  it('stays within [min, max]', () => {
    for (let i = 1; i <= 50; i++) {
      const value = randomNumber(i, 10, 20)
      expect(value).toBeGreaterThanOrEqual(10)
      expect(value).toBeLessThanOrEqual(20)
    }
  })

  it('floors the result when round is 0 (the default)', () => {
    const value = randomNumber(7, 0, 100)
    expect(Number.isInteger(value)).toBe(true)
  })

  it('rounds to the given number of digits when round is set', () => {
    const value = randomNumber(7, 0, 1, 8)
    expect(value).toBe(parseFloat(value.toFixed(8)))
  })
})

describe('randomDate', () => {
  it('returns a deterministic date within the 2024 range', () => {
    const date = randomDate(3)
    expect(date.getUTCFullYear()).toBe(2024)
    expect(date).toEqual(randomDate(3))
  })
})

describe('randomItem', () => {
  it('deterministically picks one of the given items', () => {
    const items = ['a', 'b', 'c', 'd']
    const picked = randomItem(4, items)
    expect(items).toContain(picked)
    expect(randomItem(4, items)).toBe(picked)
  })
})

describe('timeagoLabel', () => {
  it('returns "now" when the random offset is 0 days', () => {
    // index=0 -> randomNumber(0, 0, N) hits the x=0 edge case (sin/cos of 0).
    expect(timeagoLabel(0, 5)).toBe('now')
  })

  it('pluralizes "day(s) ago" based on the offset', () => {
    const label = timeagoLabel(2, 10)
    expect(label === 'now' || /^\d+ days? ago$/.test(label)).toBe(true)
  })
})