timers.test.ts

// eslint-disable-next-line @typescript-eslint/ban-ts-comment
// @ts-nocheck taken from Jest, but tsconfig doesn't allow most of the code

/**
 * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of https://github.com/facebook/jest.
 */

import { afterEach, describe, expect, it, vi } from 'vitest'
import { FakeTimers } from '../../../packages/vitest/src/integrations/timers'

class FakeDate extends Date {}

describe('FakeTimers', () => {
  afterEach(() => {
    vi.useRealTimers()
  })

  describe('construction', () => {
    it('installs setTimeout mock', () => {
      const global = { Date: FakeDate, clearTimeout, process, setTimeout }
      const timers = new FakeTimers({ global })
      timers.useFakeTimers()
      expect(global.setTimeout).not.toBe(undefined)
    })

    it('installs clearTimeout mock', () => {
      const global = { Date: FakeDate, clearTimeout, process, setTimeout }
      const timers = new FakeTimers({ global })
      timers.useFakeTimers()
      expect(global.clearTimeout).not.toBe(undefined)
    })

    it('installs setInterval mock', () => {
      const global = { Date: FakeDate, clearTimeout, process, setTimeout }
      const timers = new FakeTimers({ global })
      timers.useFakeTimers()
      expect(global.setInterval).not.toBe(undefined)
    })

    it('installs clearInterval mock', () => {
      const global = { Date: FakeDate, clearTimeout, process, setTimeout }
      const timers = new FakeTimers({ global })
      timers.useFakeTimers()
      expect(global.clearInterval).not.toBe(undefined)
    })

    it('mocks process.nextTick if it exists on global', () => {
      const origNextTick = () => {}
      const global = {
        Date: FakeDate,
        clearTimeout,
        process: {
          nextTick: origNextTick,
        },
        setTimeout,
      }
      const timers = new FakeTimers({ global })
      timers.useFakeTimers()
      expect(global.process.nextTick).not.toBe(origNextTick)
    })

    it('mocks setImmediate if it exists on global', () => {
      const origSetImmediate = () => {}
      const global = {
        Date: FakeDate,
        clearTimeout,
        process,
        setImmediate: origSetImmediate,
        setTimeout,
      }
      const timers = new FakeTimers({ global })
      timers.useFakeTimers()
      expect(global.setImmediate).not.toBe(origSetImmediate)
    })

    it('mocks clearImmediate if setImmediate is on global', () => {
      const origSetImmediate = () => {}
      const origClearImmediate = () => {}
      const global = {
        Date: FakeDate,
        clearImmediate: origClearImmediate,
        clearTimeout,
        process,
        setImmediate: origSetImmediate,
        setTimeout,
      }
      const timers = new FakeTimers({ global })
      timers.useFakeTimers()
      expect(global.clearImmediate).not.toBe(origClearImmediate)
    })
  })

  describe('runAllTicks', () => {
    it('runs all ticks, in order', () => {
      const global = {
        Date: FakeDate,
        clearTimeout,
        process: {
          nextTick: () => {},
        },
        setTimeout,
      }

      const timers = new FakeTimers({ global })
      timers.useFakeTimers()

      const runOrder = []
      const mock1 = vi.fn(() => runOrder.push('mock1'))
      const mock2 = vi.fn(() => runOrder.push('mock2'))

      global.process.nextTick(mock1)
      global.process.nextTick(mock2)

      expect(mock1).toHaveBeenCalledTimes(0)
      expect(mock2).toHaveBeenCalledTimes(0)

      timers.runAllTicks()

      expect(mock1).toHaveBeenCalledTimes(1)
      expect(mock2).toHaveBeenCalledTimes(1)
      expect(runOrder).toEqual(['mock1', 'mock2'])
    })

    it('does nothing when no ticks have been scheduled', () => {
      const nextTick = vi.fn()
      const global = {
        Date: FakeDate,
        clearTimeout,
        process: {
          nextTick,
        },
        setTimeout,
      }

      const timers = new FakeTimers({ global })
      timers.useFakeTimers()
      timers.runAllTicks()

      expect(nextTick).toHaveBeenCalledTimes(0)
    })

    it('only runs a scheduled callback once', () => {
      const global = {
        Date: FakeDate,
        clearTimeout,
        process: {
          nextTick: () => {},
        },
        setTimeout,
      }

      const timers = new FakeTimers({ global })
      timers.useFakeTimers()

      const mock1 = vi.fn()
      global.process.nextTick(mock1)
      expect(mock1).toHaveBeenCalledTimes(0)

      timers.runAllTicks()
      expect(mock1).toHaveBeenCalledTimes(1)

      timers.runAllTicks()
      expect(mock1).toHaveBeenCalledTimes(1)
    })

    it('throws before allowing infinite recursion', () => {
      const global = {
        Date: FakeDate,
        clearTimeout,
        process: {
          nextTick: () => {},
        },
        setTimeout,
      }

      const timers = new FakeTimers({ global, config: { loopLimit: 100 } })

      timers.useFakeTimers()

      global.process.nextTick(function infinitelyRecursingCallback() {
        global.process.nextTick(infinitelyRecursingCallback)
      })

      expect(() => {
        timers.runAllTicks()
      }).toThrow(
        'Aborting after running 100 timers, assuming an infinite loop!',
      )
    })
  })

  describe('runAllTimers', () => {
    it('runs all timers in order', () => {
      const global = { Date: FakeDate, clearTimeout, process, setTimeout }
      const timers = new FakeTimers({ global })
      timers.useFakeTimers()

      const runOrder = []
      const mock1 = vi.fn(() => runOrder.push('mock1'))
      const mock2 = vi.fn(() => runOrder.push('mock2'))
      const mock3 = vi.fn(() => runOrder.push('mock3'))
      const mock4 = vi.fn(() => runOrder.push('mock4'))
      const mock5 = vi.fn(() => runOrder.push('mock5'))
      const mock6 = vi.fn(() => runOrder.push('mock6'))

      global.setTimeout(mock1, 100)
      global.setTimeout(mock2, NaN)
      global.setTimeout(mock3, 0)
      const intervalHandler = global.setInterval(() => {
        mock4()
        global.clearInterval(intervalHandler)
      }, 200)
      global.setTimeout(mock5, Infinity)
      global.setTimeout(mock6, -Infinity)

      timers.runAllTimers()
      expect(runOrder).toEqual([
        'mock2',
        'mock3',
        'mock5',
        'mock6',
        'mock1',
        'mock4',
      ])
    })

    it('warns when trying to advance timers while real timers are used', () => {
      const timers = new FakeTimers({
        config: {
          rootDir: __dirname,
        },
        global,
      })
      expect(() => timers.runAllTimers()).toThrow(/Timers are not mocked/)
    })

    it('does nothing when no timers have been scheduled', () => {
      const nativeSetTimeout = vi.fn()
      const global = {
        Date: FakeDate,
        clearTimeout,
        process,
        setTimeout: nativeSetTimeout,
      }

      const timers = new FakeTimers({ global })
      timers.useFakeTimers()
      timers.runAllTimers()
    })

    it('only runs a setTimeout callback once (ever)', () => {
      const global = { Date: FakeDate, clearTimeout, process, setTimeout }
      const timers = new FakeTimers({ global })
      timers.useFakeTimers()

      const fn = vi.fn()
      global.setTimeout(fn, 0)
      expect(fn).toHaveBeenCalledTimes(0)

      timers.runAllTimers()
      expect(fn).toHaveBeenCalledTimes(1)

      timers.runAllTimers()
      expect(fn).toHaveBeenCalledTimes(1)
    })

    it('runs callbacks with arguments after the interval', () => {
      const global = { Date: FakeDate, clearTimeout, process, setTimeout }
      const timers = new FakeTimers({ global })
      timers.useFakeTimers()

      const fn = vi.fn()
      global.setTimeout(fn, 0, 'mockArg1', 'mockArg2')

      timers.runAllTimers()
      expect(fn).toHaveBeenCalledTimes(1)
      expect(fn).toHaveBeenCalledWith('mockArg1', 'mockArg2')
    })

    it('doesn\'t pass the callback to native setTimeout', () => {
      const nativeSetTimeout = vi.fn()

      const global = {
        Date: FakeDate,
        clearTimeout,
        process,
        setTimeout: nativeSetTimeout,
      }

      const timers = new FakeTimers({ global })
      // @sinonjs/fake-timers uses `setTimeout` during init to figure out if it's in Node or
      // browser env. So clear its calls before we install them into the env
      nativeSetTimeout.mockClear()
      timers.useFakeTimers()

      const mock1 = vi.fn()
      global.setTimeout(mock1, 0)

      timers.runAllTimers()
      expect(mock1).toHaveBeenCalledTimes(1)
      expect(nativeSetTimeout).toHaveBeenCalledTimes(0)
    })

    it('throws before allowing infinite recursion', () => {
      const global = { Date: FakeDate, clearTimeout, process, setTimeout }
      const timers = new FakeTimers({ global, config: { loopLimit: 100 } })
      timers.useFakeTimers()

      global.setTimeout(function infinitelyRecursingCallback() {
        global.setTimeout(infinitelyRecursingCallback, 0)
      }, 0)

      expect(() => {
        timers.runAllTimers()
      }).toThrow(
        'Aborting after running 100 timers, assuming an infinite loop!',
      )
    })

    it('also clears ticks', () => {
      const global = { Date: FakeDate, clearTimeout, process, setTimeout }
      const timers = new FakeTimers({ global })
      timers.useFakeTimers()

      const fn = vi.fn()
      global.setTimeout(() => {
        process.nextTick(fn)
      }, 0)
      expect(fn).toHaveBeenCalledTimes(0)

      timers.runAllTimers()
      expect(fn).toHaveBeenCalledTimes(1)
    })
  })

  describe('advanceTimersByTime', () => {
    it('runs timers in order', () => {
      const global = { Date: FakeDate, clearTimeout, process, setTimeout }
      const timers = new FakeTimers({ global })
      timers.useFakeTimers()

      const runOrder = []
      const mock1 = vi.fn(() => runOrder.push('mock1'))
      const mock2 = vi.fn(() => runOrder.push('mock2'))
      const mock3 = vi.fn(() => runOrder.push('mock3'))
      const mock4 = vi.fn(() => runOrder.push('mock4'))

      global.setTimeout(mock1, 100)
      global.setTimeout(mock2, 0)
      global.setTimeout(mock3, 0)
      global.setInterval(() => {
        mock4()
      }, 200)

      // Move forward to t=50
      timers.advanceTimersByTime(50)
      expect(runOrder).toEqual(['mock2', 'mock3'])

      // Move forward to t=60
      timers.advanceTimersByTime(10)
      expect(runOrder).toEqual(['mock2', 'mock3'])

      // Move forward to t=100
      timers.advanceTimersByTime(40)
      expect(runOrder).toEqual(['mock2', 'mock3', 'mock1'])

      // Move forward to t=200
      timers.advanceTimersByTime(100)
      expect(runOrder).toEqual(['mock2', 'mock3', 'mock1', 'mock4'])

      // Move forward to t=400
      timers.advanceTimersByTime(200)
      expect(runOrder).toEqual(['mock2', 'mock3', 'mock1', 'mock4', 'mock4'])
    })

    it('does nothing when no timers have been scheduled', () => {
      const global = { Date: FakeDate, clearTimeout, process, setTimeout }
      const timers = new FakeTimers({ global })
      timers.useFakeTimers()

      timers.advanceTimersByTime(100)
    })
  })

  describe('advanceTimersToNextTimer', () => {
    it('runs timers in order', () => {
      const global = { Date: FakeDate, clearTimeout, process, setTimeout }
      const timers = new FakeTimers({ global })
      timers.useFakeTimers()

      const runOrder: Array<string> = []
      const mock1 = vi.fn(() => runOrder.push('mock1'))
      const mock2 = vi.fn(() => runOrder.push('mock2'))
      const mock3 = vi.fn(() => runOrder.push('mock3'))
      const mock4 = vi.fn(() => runOrder.push('mock4'))

      global.setTimeout(mock1, 100)
      global.setTimeout(mock2, 0)
      global.setTimeout(mock3, 0)
      global.setInterval(() => {
        mock4()
      }, 200)

      timers.advanceTimersToNextTimer()
      // Move forward to t=0
      expect(runOrder).toEqual(['mock2', 'mock3'])

      timers.advanceTimersToNextTimer()
      // Move forward to t=100
      expect(runOrder).toEqual(['mock2', 'mock3', 'mock1'])

      timers.advanceTimersToNextTimer()
      // Move forward to t=200
      expect(runOrder).toEqual(['mock2', 'mock3', 'mock1', 'mock4'])

      timers.advanceTimersToNextTimer()
      // Move forward to t=400
      expect(runOrder).toEqual(['mock2', 'mock3', 'mock1', 'mock4', 'mock4'])
    })

    it('run correct amount of steps', () => {
      const global = { Date: FakeDate, clearTimeout, process, setTimeout }
      const timers = new FakeTimers({ global })
      timers.useFakeTimers()

      const runOrder: Array<string> = []
      const mock1 = vi.fn(() => runOrder.push('mock1'))
      const mock2 = vi.fn(() => runOrder.push('mock2'))
      const mock3 = vi.fn(() => runOrder.push('mock3'))
      const mock4 = vi.fn(() => runOrder.push('mock4'))

      global.setTimeout(mock1, 100)
      global.setTimeout(mock2, 0)
      global.setTimeout(mock3, 0)
      global.setInterval(() => {
        mock4()
      }, 200)

      // Move forward to t=100
      timers.advanceTimersToNextTimer(2)
      expect(runOrder).toEqual(['mock2', 'mock3', 'mock1'])

      // Move forward to t=600
      timers.advanceTimersToNextTimer(3)
      expect(runOrder).toEqual([
        'mock2',
        'mock3',
        'mock1',
        'mock4',
        'mock4',
        'mock4',
      ])
    })

    it('setTimeout inside setTimeout', () => {
      const global = { Date: FakeDate, clearTimeout, process, setTimeout }
      const timers = new FakeTimers({ global })
      timers.useFakeTimers()

      const runOrder: Array<string> = []
      const mock1 = vi.fn(() => runOrder.push('mock1'))
      const mock2 = vi.fn(() => runOrder.push('mock2'))
      const mock3 = vi.fn(() => runOrder.push('mock3'))
      const mock4 = vi.fn(() => runOrder.push('mock4'))

      global.setTimeout(mock1, 0)
      global.setTimeout(() => {
        mock2()
        global.setTimeout(mock3, 50)
      }, 25)
      global.setTimeout(mock4, 100)

      // Move forward to t=75
      timers.advanceTimersToNextTimer(3)
      expect(runOrder).toEqual(['mock1', 'mock2', 'mock3'])
    })

    it('does nothing when no timers have been scheduled', () => {
      const global = { Date: FakeDate, clearTimeout, process, setTimeout }
      const timers = new FakeTimers({ global })
      timers.useFakeTimers()

      timers.advanceTimersToNextTimer()
    })
  })

  describe('reset', () => {
    it('resets all pending setTimeouts', () => {
      const global = { Date: FakeDate, clearTimeout, process, setTimeout }
      const timers = new FakeTimers({ global })
      timers.useFakeTimers()

      const mock1 = vi.fn()
      global.setTimeout(mock1, 100)

      timers.reset()
      timers.runAllTimers()
      expect(mock1).toHaveBeenCalledTimes(0)
    })

    it('resets all pending setIntervals', () => {
      const global = { Date: FakeDate, clearTimeout, process, setTimeout }
      const timers = new FakeTimers({ global })
      timers.useFakeTimers()

      const mock1 = vi.fn()
      global.setInterval(mock1, 200)

      timers.reset()
      timers.runAllTimers()
      expect(mock1).toHaveBeenCalledTimes(0)
    })

    it('resets all pending ticks callbacks', () => {
      const global = {
        Date: FakeDate,
        clearTimeout,
        process: {
          nextTick: () => {},
        },
        setImmediate: () => {},
        setTimeout,
      }
      const timers = new FakeTimers({ global })
      timers.useFakeTimers()

      const mock1 = vi.fn()
      global.process.nextTick(mock1)
      global.setImmediate(mock1)

      timers.reset()
      timers.runAllTicks()
      expect(mock1).toHaveBeenCalledTimes(0)
    })

    it('resets current advanceTimersByTime time cursor', () => {
      const global = { Date: FakeDate, clearTimeout, process, setTimeout }
      const timers = new FakeTimers({ global })
      timers.useFakeTimers()

      const mock1 = vi.fn()
      global.setTimeout(mock1, 100)
      timers.advanceTimersByTime(50)

      timers.reset()
      global.setTimeout(mock1, 100)

      timers.advanceTimersByTime(50)
      expect(mock1).toHaveBeenCalledTimes(0)
    })
  })

  describe('runOnlyPendingTimers', () => {
    it('runs all timers in order', () => {
      const nativeSetImmediate = vi.fn()

      const global = {
        Date: FakeDate,
        clearTimeout,
        process,
        setImmediate: nativeSetImmediate,
        setTimeout,
      }

      const timers = new FakeTimers({ global })
      timers.useFakeTimers()

      const runOrder = []

      global.setTimeout(function cb() {
        runOrder.push('mock1')
        global.setTimeout(cb, 100)
      }, 100)

      global.setTimeout(function cb() {
        runOrder.push('mock2')
        global.setTimeout(cb, 50)
      }, 0)

      global.setInterval(() => {
        runOrder.push('mock3')
      }, 200)

      global.setImmediate(() => {
        runOrder.push('mock4')
      })

      global.setImmediate(function cb() {
        runOrder.push('mock5')
        global.setTimeout(cb, 400)
      })

      timers.runOnlyPendingTimers()
      const firsRunOrder = [
        'mock4',
        'mock5',
        'mock2',
        'mock2',
        'mock1',
        'mock2',
        'mock2',
        'mock3',
        'mock1',
        'mock2',
      ]

      expect(runOrder).toEqual(firsRunOrder)

      timers.runOnlyPendingTimers()
      expect(runOrder).toEqual([
        ...firsRunOrder,
        'mock2',
        'mock1',
        'mock2',
        'mock2',
        'mock3',
        'mock5',
        'mock1',
        'mock2',
      ])
    })

    it('does not run timers that were cleared in another timer', () => {
      const global = { Date: FakeDate, clearTimeout, process, setTimeout }
      const timers = new FakeTimers({ global })
      timers.useFakeTimers()

      const fn = vi.fn()
      const timer = global.setTimeout(fn, 10)
      global.setTimeout(() => {
        global.clearTimeout(timer)
      }, 0)

      timers.runOnlyPendingTimers()
      expect(fn).not.toBeCalled()
    })
  })

  describe('useRealTimers', () => {
    it('resets native timer APIs', () => {
      const nativeSetTimeout = vi.fn()
      const nativeSetInterval = vi.fn()
      const nativeClearTimeout = vi.fn()
      const nativeClearInterval = vi.fn()

      const global = {
        Date: FakeDate,
        clearInterval: nativeClearInterval,
        clearTimeout: nativeClearTimeout,
        process,
        setInterval: nativeSetInterval,
        setTimeout: nativeSetTimeout,
      }
      const timers = new FakeTimers({ global })
      timers.useFakeTimers()

      // Ensure that timers has overridden the native timer APIs
      // (because if it didn't, this test might pass when it shouldn't)
      expect(global.setTimeout).not.toBe(nativeSetTimeout)
      expect(global.setInterval).not.toBe(nativeSetInterval)
      expect(global.clearTimeout).not.toBe(nativeClearTimeout)
      expect(global.clearInterval).not.toBe(nativeClearInterval)

      timers.useRealTimers()

      expect(global.setTimeout).toBe(nativeSetTimeout)
      expect(global.setInterval).toBe(nativeSetInterval)
      expect(global.clearTimeout).toBe(nativeClearTimeout)
      expect(global.clearInterval).toBe(nativeClearInterval)
    })

    it('resets native process.nextTick when present', () => {
      const nativeProcessNextTick = vi.fn()

      const global = {
        Date: FakeDate,
        clearTimeout,
        process: { nextTick: nativeProcessNextTick },
        setTimeout,
      }
      const timers = new FakeTimers({ global })
      timers.useFakeTimers()

      // Ensure that timers has overridden the native timer APIs
      // (because if it didn't, this test might pass when it shouldn't)
      expect(global.process.nextTick).not.toBe(nativeProcessNextTick)

      timers.useRealTimers()

      expect(global.process.nextTick).toBe(nativeProcessNextTick)
    })

    it('resets native setImmediate when present', () => {
      const nativeSetImmediate = vi.fn()
      const nativeClearImmediate = vi.fn()

      const global = {
        Date: FakeDate,
        clearImmediate: nativeClearImmediate,
        clearTimeout,
        process,
        setImmediate: nativeSetImmediate,
        setTimeout,
      }
      const timers = new FakeTimers({ global })
      timers.useFakeTimers()

      // Ensure that timers has overridden the native timer APIs
      // (because if it didn't, this test might pass when it shouldn't)
      expect(global.setImmediate).not.toBe(nativeSetImmediate)
      expect(global.clearImmediate).not.toBe(nativeClearImmediate)

      timers.useRealTimers()

      expect(global.setImmediate).toBe(nativeSetImmediate)
      expect(global.clearImmediate).toBe(nativeClearImmediate)
    })
  })

  describe('useFakeTimers', () => {
    it('resets mock timer APIs', () => {
      const nativeSetTimeout = vi.fn()
      const nativeSetInterval = vi.fn()
      const nativeClearTimeout = vi.fn()
      const nativeClearInterval = vi.fn()

      const global = {
        Date: FakeDate,
        clearInterval: nativeClearInterval,
        clearTimeout: nativeClearTimeout,
        process,
        setInterval: nativeSetInterval,
        setTimeout: nativeSetTimeout,
      }
      const timers = new FakeTimers({ global })
      timers.useRealTimers()

      // Ensure that the real timers are installed at this point
      // (because if they aren't, this test might pass when it shouldn't)
      expect(global.setTimeout).toBe(nativeSetTimeout)
      expect(global.setInterval).toBe(nativeSetInterval)
      expect(global.clearTimeout).toBe(nativeClearTimeout)
      expect(global.clearInterval).toBe(nativeClearInterval)

      timers.useFakeTimers()

      expect(global.setTimeout).not.toBe(nativeSetTimeout)
      expect(global.setInterval).not.toBe(nativeSetInterval)
      expect(global.clearTimeout).not.toBe(nativeClearTimeout)
      expect(global.clearInterval).not.toBe(nativeClearInterval)
    })

    it('resets mock process.nextTick when present', () => {
      const nativeProcessNextTick = vi.fn()

      const global = {
        Date: FakeDate,
        clearTimeout,
        process: { nextTick: nativeProcessNextTick },
        setTimeout,
      }
      const timers = new FakeTimers({ global })
      timers.useRealTimers()

      // Ensure that the real timers are installed at this point
      // (because if they aren't, this test might pass when it shouldn't)
      expect(global.process.nextTick).toBe(nativeProcessNextTick)

      timers.useFakeTimers()

      expect(global.process.nextTick).not.toBe(nativeProcessNextTick)
    })

    it('resets mock setImmediate when present', () => {
      const nativeSetImmediate = vi.fn()
      const nativeClearImmediate = vi.fn()

      const global = {
        Date: FakeDate,
        clearImmediate: nativeClearImmediate,
        clearTimeout,
        process,
        setImmediate: nativeSetImmediate,
        setTimeout,
      }
      const fakeTimers = new FakeTimers({ global })
      fakeTimers.useRealTimers()

      // Ensure that the real timers are installed at this point
      // (because if they aren't, this test might pass when it shouldn't)
      expect(global.setImmediate).toBe(nativeSetImmediate)
      expect(global.clearImmediate).toBe(nativeClearImmediate)

      fakeTimers.useFakeTimers()

      expect(global.setImmediate).not.toBe(nativeSetImmediate)
      expect(global.clearImmediate).not.toBe(nativeClearImmediate)
    })
  })

  describe('getTimerCount', () => {
    it('returns the correct count', () => {
      const timers = new FakeTimers({ global })

      timers.useFakeTimers()

      global.setTimeout(() => {}, 0)
      global.setTimeout(() => {}, 0)
      global.setTimeout(() => {}, 10)

      expect(timers.getTimerCount()).toEqual(3)

      timers.advanceTimersByTime(5)

      expect(timers.getTimerCount()).toEqual(1)

      timers.advanceTimersByTime(5)

      expect(timers.getTimerCount()).toEqual(0)

      timers.useRealTimers()
    })

    it('includes immediates and ticks', () => {
      const timers = new FakeTimers({ global })

      timers.useFakeTimers()

      global.setTimeout(() => {}, 0)
      global.setImmediate(() => {})
      process.nextTick(() => {})

      expect(timers.getTimerCount()).toEqual(3)

      timers.useRealTimers()
    })

    it('not includes cancelled immediates', () => {
      const timers = new FakeTimers({ global })

      timers.useFakeTimers()

      global.setImmediate(() => {})
      expect(timers.getTimerCount()).toEqual(1)
      timers.clearAllTimers()

      expect(timers.getTimerCount()).toEqual(0)

      timers.useRealTimers()
    })

    it('throws when using useFakeTimers after setSystemTime', () => {
      const timers = new FakeTimers({ global })

      const timeStr = 'Fri Feb 20 2015 19:29:31 GMT+0530'
      const timeStrMs = 1424440771000

      timers.setSystemTime(timeStr)

      expect(Date.now()).toBe(timeStrMs)

      expect(() => timers.useFakeTimers()).toThrowError(/date was mocked/)

      // Some test

      timers.useRealTimers()
    })
  })
})