import { getMutex } from '../mutex'

describe('getMutex', () => {
  it('executes read/writes in order', async () => {
    const mutex = getMutex()
    let i = 1
    const inc = async () => {
      const [lock, release] = mutex.getLock()
      await lock

      // read current value
      const temp = i

      // Async action: give control flow to the next function before changing value
      await Promise.resolve()
      i = temp + 1

      release()
    }
    await Promise.all([inc(), inc(), inc(), inc()])
    await inc()
    expect(i).toBe(6)
  })
})