import { describe, it } from 'node:test'
import assert from 'node:assert/strict'
import { addMonthsYmd } from './oa-confirmation-date'

describe('addMonthsYmd', () => {
  it('simple month add', () => {
    assert.equal(addMonthsYmd('2026-01-15', 3), '2026-04-15')
  })

  it('clamp end of month', () => {
    assert.equal(addMonthsYmd('2026-01-31', 1), '2026-02-28')
  })

  it('zero months returns same day', () => {
    assert.equal(addMonthsYmd('2026-07-30', 0), '2026-07-30')
  })

  it('invalid => null', () => {
    assert.equal(addMonthsYmd('', 3), null)
    assert.equal(addMonthsYmd('2026-01-15', -1), null)
  })
})