scheduler_test.go

package gocron

import (
	"fmt"
	"log"
	"sync"
	"sync/atomic"
	"testing"
	"time"

	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

var _ timeWrapper = (*fakeTime)(nil)

type fakeTime struct {
	onNow func(location *time.Location) time.Time
}

func (f fakeTime) Now(loc *time.Location) time.Time {
	return f.onNow(loc)
}

func (f fakeTime) Unix(i int64, i2 int64) time.Time {
	panic("implement me")
}

func (f fakeTime) Sleep(duration time.Duration) {
	panic("implement me")
}

func task() {
	fmt.Println("I am a running job.")
}

func taskWithParams(a int, b string) {
	fmt.Println(a, b)
}

func TestImmediateExecution(t *testing.T) {
	s := NewScheduler(time.UTC)
	semaphore := make(chan bool)
	_, err := s.Every(1).Second().Do(func() {
		semaphore <- true
	})
	require.NoError(t, err)
	s.StartAsync()
	select {
	case <-time.After(1 * time.Second):
		t.Fatal("job did not run immediately")
	case <-semaphore:
		// test passed
	}

}

func TestScheduler_Every_InvalidInterval(t *testing.T) {
	testCases := []struct {
		description   string
		interval      interface{}
		expectedError string
	}{
		{"zero", 0, ErrInvalidInterval.Error()},
		{"negative", -1, ErrInvalidInterval.Error()},
		{"invalid string duration", "bad", "time: invalid duration \"bad\""},
	}

	s := NewScheduler(time.UTC)

	for _, tc := range testCases {
		t.Run(tc.description, func(t *testing.T) {
			_, err := s.Every(tc.interval).Do(func() {})
			require.Error(t, err)
			assert.EqualError(t, err, tc.expectedError)
		})
	}

}

func TestScheduler_Every(t *testing.T) {
	t.Run("time.Duration", func(t *testing.T) {
		s := NewScheduler(time.UTC)
		semaphore := make(chan bool)

		_, err := s.Every(100 * time.Millisecond).Do(func() {
			semaphore <- true
		})
		require.NoError(t, err)

		s.StartAsync()

		var counter int

		now := time.Now()
		for time.Now().Before(now.Add(500 * time.Millisecond)) {
			if <-semaphore {
				counter++
			}
		}
		s.Stop()
		assert.Equal(t, 6, counter)
	})

	t.Run("int", func(t *testing.T) {
		s := NewScheduler(time.UTC)
		semaphore := make(chan bool)

		_, err := s.Every(100).Milliseconds().Do(func() {
			semaphore <- true
		})
		require.NoError(t, err)

		s.StartAsync()

		var counter int

		now := time.Now()
		for time.Now().Before(now.Add(100 * time.Millisecond)) {
			if <-semaphore {
				counter++
			}
		}
		s.Stop()
		assert.Equal(t, 2, counter)
	})

	t.Run("string duration", func(t *testing.T) {
		s := NewScheduler(time.UTC)
		semaphore := make(chan bool)

		_, err := s.Every("100ms").Do(func() {
			semaphore <- true
		})
		require.NoError(t, err)

		s.StartAsync()

		var counter int

		now := time.Now()
		for time.Now().Before(now.Add(100 * time.Millisecond)) {
			if <-semaphore {
				counter++
			}
		}
		s.Stop()
		assert.Equal(t, 2, counter)
	})

}

func TestExecutionSeconds(t *testing.T) {
	s := NewScheduler(time.UTC)
	jobDone := make(chan bool)

	var (
		executions         []int64
		interval           = 1
		expectedExecutions = 2
		mu                 sync.RWMutex
	)

	runTime := 1 * time.Second
	startTime := time.Now()

	// default unit is seconds
	_, err := s.Every(interval).Do(func() {
		mu.Lock()
		defer mu.Unlock()
		executions = append(executions, time.Now().UTC().Unix())
		if time.Now().After(startTime.Add(runTime)) {
			jobDone <- true
		}
	})
	require.NoError(t, err)

	s.StartAsync()
	<-jobDone // Wait job done
	s.Stop()

	mu.RLock()
	defer mu.RUnlock()
	assert.Equal(t, expectedExecutions, len(executions), "did not run expected number of times")

	for i := 1; i < expectedExecutions; i++ {
		durationBetweenExecutions := executions[i] - executions[i-1]
		assert.Equal(t, int64(interval), durationBetweenExecutions, "duration between tasks does not correspond to expectations")
	}
}

func TestScheduled(t *testing.T) {
	t.Run("simple", func(t *testing.T) {
		s := NewScheduler(time.UTC)
		_, err := s.Every(1).Second().Do(task)
		require.NoError(t, err)
		assert.True(t, s.TaskPresent(task))
	})

	t.Run("with tag", func(t *testing.T) {
		s := NewScheduler(time.UTC)
		_, err := s.Every(1).Hour().Tag("my_custom_tag").Do(task)
		require.NoError(t, err)
		assert.True(t, s.TaskPresent(task))
	})
}

func TestAt(t *testing.T) {
	t.Run("job scheduled for future hasn't run yet", func(t *testing.T) {
		ft := fakeTime{onNow: func(l *time.Location) time.Time {
			return time.Date(1970, 1, 1, 12, 0, 0, 0, l)
		}}

		s := NewScheduler(time.UTC)
		s.time = ft
		now := ft.onNow(time.UTC)
		semaphore := make(chan bool)

		nextMinuteTime := now.Add(1 * time.Minute)
		startAt := fmt.Sprintf("%02d:%02d:%02d", nextMinuteTime.Hour(), nextMinuteTime.Minute(), nextMinuteTime.Second())
		dayJob, err := s.Every(1).Day().At(startAt).Do(func() {
			semaphore <- true
		})
		require.NoError(t, err)

		s.StartAsync()
		time.Sleep(1 * time.Second)

		select {
		case <-time.After(1 * time.Second):
			log.Println(now.Add(time.Minute))
			log.Println(dayJob.nextRun)
			assert.Equal(t, now.Add(1*time.Minute), dayJob.nextRun)
		case <-semaphore:
			t.Fatal("job ran even though scheduled in future")
		}
	})

	t.Run("error due to bad time format", func(t *testing.T) {
		s := NewScheduler(time.UTC)
		badTime := "0:0"
		_, err := s.Every(1).Day().At(badTime).Do(func() {})
		assert.EqualError(t, err, ErrUnsupportedTimeFormat.Error())
		assert.Zero(t, s.Len())
	})
}

func schedulerForNextOrPreviousWeekdayEveryNTimes(weekday time.Weekday, next bool, n int, s *Scheduler) *Scheduler {
	switch weekday {
	case time.Monday:
		if next {
			s = s.Every(n).Tuesday()
		} else {
			s = s.Every(n).Sunday()
		}
	case time.Tuesday:
		if next {
			s = s.Every(n).Wednesday()
		} else {
			s = s.Every(n).Monday()
		}
	case time.Wednesday:
		if next {
			s = s.Every(n).Thursday()
		} else {
			s = s.Every(n).Tuesday()
		}
	case time.Thursday:
		if next {
			s = s.Every(n).Friday()
		} else {
			s = s.Every(n).Wednesday()
		}
	case time.Friday:
		if next {
			s = s.Every(n).Saturday()
		} else {
			s = s.Every(n).Thursday()
		}
	case time.Saturday:
		if next {
			s = s.Every(n).Sunday()
		} else {
			s = s.Every(n).Friday()
		}
	case time.Sunday:
		if next {
			s = s.Every(n).Monday()
		} else {
			s = s.Every(n).Saturday()
		}
	}
	return s
}

func TestWeekdayBeforeToday(t *testing.T) {
	now := time.Now().In(time.UTC)
	s := NewScheduler(time.UTC)

	s = schedulerForNextOrPreviousWeekdayEveryNTimes(now.Weekday(), false, 1, s)
	weekJob, err := s.Do(task)
	require.NoError(t, err)
	s.scheduleNextRun(weekJob)
	sixDaysFromNow := now.AddDate(0, 0, 6)

	exp := time.Date(sixDaysFromNow.Year(), sixDaysFromNow.Month(), sixDaysFromNow.Day(), 0, 0, 0, 0, time.UTC)
	assert.Equal(t, exp, weekJob.nextRun)
}

func TestWeekdayAt(t *testing.T) {
	t.Run("asserts weekday scheduling starts at the current week", func(t *testing.T) {
		s := NewScheduler(time.UTC)
		now := time.Now().UTC()
		s = schedulerForNextOrPreviousWeekdayEveryNTimes(now.Weekday(), true, 1, s)
		weekdayJob, _ := s.Do(task)

		s.scheduleNextRun(weekdayJob)

		tomorrow := now.AddDate(0, 0, 1)
		exp := time.Date(tomorrow.Year(), tomorrow.Month(), tomorrow.Day(), 0, 0, 0, 0, time.UTC)
		nextRun := weekdayJob.nextRun
		nextRunDate := time.Date(nextRun.Year(), nextRun.Month(), nextRun.Day(), 0, 0, 0, 0, time.UTC)
		assert.Equal(t, exp, nextRunDate)
	})
}

func TestScheduler_Remove(t *testing.T) {

	t.Run("remove from non-running", func(t *testing.T) {
		s := NewScheduler(time.UTC)
		s.TagsUnique()
		_, err := s.Every(1).Minute().Tag("tag1").Do(task)
		require.NoError(t, err)
		_, err = s.Every(1).Minute().Do(taskWithParams, 1, "hello")
		require.NoError(t, err)
		_, err = s.Every(1).Minute().Do(task)
		require.NoError(t, err)

		assert.Equal(t, 3, s.Len(), "Incorrect number of jobs")

		s.Remove(task)
		assert.Equal(t, 1, s.Len(), "Incorrect number of jobs after removing 2 job")

		s.Remove(task)
		assert.Equal(t, 1, s.Len(), "Incorrect number of jobs after removing non-existent job")
	})

	t.Run("remove from running scheduler", func(t *testing.T) {
		s := NewScheduler(time.UTC)
		semaphore := make(chan bool)

		j, err := s.Every("100ms").StartAt(s.time.Now(s.location).Add(time.Second)).Do(func() {
			semaphore <- true
		})
		require.NoError(t, err)

		s.StartAsync()

		s.Remove(j.function)

		select {
		case <-time.After(200 * time.Millisecond):
			// test passed
		case <-semaphore:
			t.Fatal("job ran after being removed")
		}
	})
}

func TestScheduler_RemoveByReference(t *testing.T) {
	t.Run("remove from non-running scheduler", func(t *testing.T) {
		s := NewScheduler(time.UTC)
		job1, _ := s.Every(1).Minute().Do(task)
		job2, _ := s.Every(1).Minute().Do(taskWithParams, 1, "hello")

		assert.Equal(t, 2, s.Len(), "Incorrect number of jobs")

		s.RemoveByReference(job1)
		assert.ElementsMatch(t, []*Job{job2}, s.Jobs())
	})

	t.Run("remove from running scheduler", func(t *testing.T) {
		s := NewScheduler(time.UTC)
		s.TagsUnique()
		semaphore := make(chan bool)

		j, err := s.Every("100ms").StartAt(s.time.Now(s.location).Add(100 * time.Millisecond)).Tag("tag1").Do(func() {
			semaphore <- true
		})
		require.NoError(t, err)

		s.StartAsync()

		s.RemoveByReference(j)

		select {
		case <-time.After(200 * time.Millisecond):
			// test passed
		case <-semaphore:
			t.Fatal("job ran after being removed")
		}

		_, ok := s.tags.Load("tag1")
		assert.False(t, ok)
	})
}

func TestScheduler_RemoveByTag(t *testing.T) {
	t.Run("non unique tags", func(t *testing.T) {
		s := NewScheduler(time.UTC)

		// Creating 2 Jobs with different tags
		tag1 := "a"
		tag2 := "ab"
		_, err := s.Every(1).Second().Tag(tag1).Do(taskWithParams, 1, "hello") // index 0
		require.NoError(t, err)
		_, err = s.Every(1).Second().Tag(tag2).Do(taskWithParams, 2, "world") // index 1
		require.NoError(t, err)

		// check Jobs()[0] tags is equal with tag "a" (tag1)
		assert.Equal(t, s.Jobs()[0].Tags()[0], tag1, "Job With Tag 'a' is removed from index 0")

		err = s.RemoveByTag(tag1)
		require.NoError(t, err)
		assert.Equal(t, 1, s.Len(), "Incorrect number of jobs after removing 1 job")

		// check Jobs()[0] tags is equal with tag "tag two" (tag2) after removing "a"
		assert.Equal(t, s.Jobs()[0].Tags()[0], tag2, "Job With Tag 'tag two' is removed from index 0")

		// Removing Non Existent Job with "a" because already removed above (will not removing any jobs because tag not match)
		err = s.RemoveByTag(tag1)
		assert.EqualError(t, err, ErrJobNotFoundWithTag.Error())
	})

	t.Run("unique tags", func(t *testing.T) {
		s := NewScheduler(time.UTC)
		s.TagsUnique()

		// Creating 2 Jobs with unique tags
		tag1 := "tag one"
		tag2 := "tag two"
		_, err := s.Every(1).Second().Tag(tag1).Do(taskWithParams, 1, "hello") // index 0
		require.NoError(t, err)
		_, err = s.Every(1).Second().Tag(tag2).Do(taskWithParams, 2, "world") // index 1
		require.NoError(t, err)

		err = s.RemoveByTag("tag one")
		require.NoError(t, err)

		// Adding job with tag after removing by tag, assuming the unique tag has been removed as well
		_, err = s.Every(1).Second().Tag(tag1).Do(taskWithParams, 1, "hello")
		assert.Nil(t, err, "Unique tag is not deleted when removing by tag")
	})
}

func TestScheduler_Jobs(t *testing.T) {
	s := NewScheduler(time.UTC)
	s.Every(1).Minute().Do(task)
	s.Every(2).Minutes().Do(task)
	s.Every(3).Minutes().Do(task)
	s.Every(4).Minutes().Do(task)
	js := s.Jobs()
	assert.Len(t, js, 4)
}

func TestScheduler_Len(t *testing.T) {
	s := NewScheduler(time.UTC)
	s.Every(1).Minute().Do(task)
	s.Every(2).Minutes().Do(task)
	s.Every(3).Minutes().Do(task)
	s.Every(4).Minutes().Do(task)
	l := s.Len()

	assert.Equal(t, l, 4)
}

func TestSwap(t *testing.T) {
	s := NewScheduler(time.UTC)
	_, err := s.Every(1).Minute().Do(task)
	require.NoError(t, err)
	_, err = s.Every(2).Minute().Do(task)
	require.NoError(t, err)

	jb := s.Jobs()
	var jobsBefore []*Job
	jobsBefore = append(jobsBefore, jb...)

	s.Swap(1, 0)

	jobsAfter := s.Jobs()

	assert.Equal(t, jobsBefore[0], jobsAfter[1])
	assert.Equal(t, jobsBefore[1], jobsAfter[0])
}

func TestLess(t *testing.T) {
	s := NewScheduler(time.UTC)
	s.Every(1).Minute().Do(task)
	s.Every(2).Minute().Do(task)

	assert.True(t, s.Less(0, 1))
}

func TestSetLocation(t *testing.T) {
	s := NewScheduler(time.FixedZone("UTC-8", -8*60*60))

	assert.Equal(t, time.FixedZone("UTC-8", -8*60*60), s.Location())

	s.ChangeLocation(time.UTC)

	assert.Equal(t, time.UTC, s.Location())
}

func TestClear(t *testing.T) {
	s := NewScheduler(time.UTC)
	semaphore := make(chan bool)

	_, err := s.Every("100ms").Do(func() {
		semaphore <- true
	})
	require.NoError(t, err)

	s.StartAsync()

	s.Clear()
	assert.Equal(t, 0, s.Len())

	var counter int
	now := time.Now()
	for time.Now().Before(now.Add(200 * time.Millisecond)) {
		select {
		case <-semaphore:
			counter++
		default:
		}
	}

	// job should run only once - immediately and then
	// be stopped on s.Clear()
	assert.Equal(t, 1, counter)
}

func TestClearUnique(t *testing.T) {
	s := NewScheduler(time.UTC)
	s.TagsUnique()
	semaphore := make(chan bool)

	_, err := s.Every("100ms").Tag("tag1").Do(func() {
		semaphore <- true
	})
	require.NoError(t, err)

	s.StartAsync()

	s.Clear()
	assert.Equal(t, 0, s.Len())

	var counter int
	now := time.Now()
	for time.Now().Before(now.Add(200 * time.Millisecond)) {
		select {
		case <-semaphore:
			counter++
		default:
		}
	}

	// job should run only once - immediately and then
	// be stopped on s.Clear()
	assert.Equal(t, 1, counter)

	s.tags.Range(func(key, value interface{}) bool {
		assert.FailNow(t, "map should be empty")
		return true
	})
}

func TestSetUnit(t *testing.T) {

	testCases := []struct {
		desc     string
		timeUnit schedulingUnit
	}{
		{"seconds", seconds},
		{"minutes", minutes},
		{"hours", hours},
		{"days", days},
		{"weeks", weeks},
	}

	for _, tc := range testCases {
		s := NewScheduler(time.UTC)
		t.Run(tc.desc, func(t *testing.T) {
			switch tc.timeUnit {
			case seconds:
				s.Every(2).Seconds().Do(task)
			case minutes:
				s.Every(2).Minutes().Do(task)
			case hours:
				s.Every(2).Hours().Do(task)
			case days:
				s.Every(2).Days().Do(task)
			case weeks:
				s.Every(2).Weeks().Do(task)
			}
			j := s.jobs[0]

			assert.Equal(t, tc.timeUnit, j.unit)
		})
	}
}

func TestScheduler_Stop(t *testing.T) {
	t.Run("stops a running scheduler", func(t *testing.T) {
		s := NewScheduler(time.UTC)
		s.StartAsync()
		assert.True(t, s.IsRunning())
		s.Stop()
		assert.False(t, s.IsRunning())
	})
	t.Run("stops a running scheduler calling .Stop()", func(t *testing.T) {
		s := NewScheduler(time.UTC)
		s.StartAsync()
		assert.True(t, s.IsRunning())
		s.Stop()
		time.Sleep(1 * time.Millisecond) // wait for stop goroutine to catch up
		assert.False(t, s.IsRunning())
	})
	t.Run("noop on stopped scheduler", func(t *testing.T) {
		s := NewScheduler(time.UTC)
		s.Stop()
		assert.False(t, s.IsRunning())
	})
	t.Run("waits for jobs to finish processing before returning .Stop()", func(t *testing.T) {
		t.Parallel()
		i := int32(0)

		s := NewScheduler(time.UTC)
		s.Every(10).Second().Do(func() {
			time.Sleep(2 * time.Second)
			atomic.AddInt32(&i, 1)
		})
		s.StartAsync()
		time.Sleep(1 * time.Second) // enough time for job to run
		s.Stop()

		assert.EqualValues(t, 1, atomic.LoadInt32(&i))
	})
}

func TestScheduler_StartAt(t *testing.T) {
	t.Run("scheduling", func(t *testing.T) {
		s := NewScheduler(time.Local)
		now := time.Now()

		// With StartAt
		job, _ := s.Every(3).Seconds().StartAt(now.Add(time.Second * 5)).Do(func() {})
		assert.False(t, job.getStartsImmediately())
		s.start()
		assert.Equal(t, now.Add(time.Second*5).Truncate(time.Second), job.NextRun().Truncate(time.Second))
		s.stop()

		// Without StartAt
		job, _ = s.Every(3).Seconds().Do(func() {})
		assert.True(t, job.getStartsImmediately())
	})

	t.Run("run", func(t *testing.T) {
		s := NewScheduler(time.UTC)
		semaphore := make(chan bool)

		s.Every(1).Day().StartAt(s.time.Now(s.location).Add(100 * time.Millisecond)).Do(func() {
			semaphore <- true
		})

		s.StartAsync()

		select {
		case <-time.After(200 * time.Millisecond):
			t.Fatal("job did not run at 1 second")
		case <-semaphore:
			// test passed
		}
	})

	t.Run("start in past", func(t *testing.T) {
		s := NewScheduler(time.Local)
		now := time.Now()

		// Start 5 seconds ago and make sure next run is in the future
		job, _ := s.Every(24).Hours().StartAt(now.Add(-24 * time.Hour).Add(10 * time.Minute)).Do(func() {})
		assert.False(t, job.getStartsImmediately())
		s.start()
		assert.Equal(t, now.Add(10*time.Minute).Truncate(time.Second), job.NextRun().Truncate(time.Second))
		s.stop()
	})
}

func TestScheduler_CalculateNextRun(t *testing.T) {
	ft := fakeTime{onNow: func(l *time.Location) time.Time {
		return time.Date(1970, 1, 1, 12, 0, 0, 0, l)
	}}

	day := time.Hour * 24
	januaryFirst2020At := func(hour, minute, second int) time.Time {
		return time.Date(2020, time.January, 1, hour, minute, second, 0, time.UTC)
	}
	mondayAt := func(hour, minute, second int) time.Time {
		return time.Date(2020, time.January, 6, hour, minute, second, 0, time.UTC)
	}

	testCases := []struct {
		name                 string
		job                  *Job
		wantTimeUntilNextRun time.Duration
	}{
		// SECONDS
		{name: "every second test", job: &Job{interval: 1, unit: seconds, lastRun: januaryFirst2020At(0, 0, 0)}, wantTimeUntilNextRun: _getSeconds(1)},
		{name: "every 62 seconds test", job: &Job{interval: 62, unit: seconds, lastRun: januaryFirst2020At(0, 0, 0)}, wantTimeUntilNextRun: _getSeconds(62)},
		// MINUTES
		{name: "every minute test", job: &Job{interval: 1, unit: minutes, lastRun: januaryFirst2020At(0, 0, 0)}, wantTimeUntilNextRun: _getMinutes(1)},
		{name: "every 62 minutes test", job: &Job{interval: 62, unit: minutes, lastRun: januaryFirst2020At(0, 0, 0)}, wantTimeUntilNextRun: _getMinutes(62)},
		// HOURS
		{name: "every hour test", job: &Job{interval: 1, unit: hours, lastRun: januaryFirst2020At(0, 0, 0)}, wantTimeUntilNextRun: _getHours(1)},
		{name: "every 25 hours test", job: &Job{interval: 25, unit: hours, lastRun: januaryFirst2020At(0, 0, 0)}, wantTimeUntilNextRun: _getHours(25)},
		// DAYS
		{name: "every day at midnight", job: &Job{interval: 1, unit: days, lastRun: januaryFirst2020At(0, 0, 0)}, wantTimeUntilNextRun: 1 * day},
		{name: "every day at 09:30AM with scheduler starting before 09:30AM should run at same day at time", job: &Job{interval: 1, unit: days, atTime: _getHours(9) + _getMinutes(30), lastRun: januaryFirst2020At(0, 0, 0)}, wantTimeUntilNextRun: _getHours(9) + _getMinutes(30)},
		{name: "every day at 09:30AM which just ran should run tomorrow at 09:30AM", job: &Job{interval: 1, unit: days, atTime: _getHours(9) + _getMinutes(30), lastRun: januaryFirst2020At(9, 30, 0)}, wantTimeUntilNextRun: 1 * day},
		{name: "every 31 days at midnight should run 31 days later", job: &Job{interval: 31, unit: days, lastRun: januaryFirst2020At(0, 0, 0)}, wantTimeUntilNextRun: 31 * day},
		{name: "daily job just ran at 8:30AM and should be scheduled for next day's 8:30AM", job: &Job{interval: 1, unit: days, atTime: 8*time.Hour + 30*time.Minute, lastRun: januaryFirst2020At(8, 30, 0)}, wantTimeUntilNextRun: 24 * time.Hour},
		{name: "daily job just ran at 5:30AM and should be scheduled for today at 8:30AM", job: &Job{interval: 1, unit: days, atTime: 8*time.Hour + 30*time.Minute, lastRun: januaryFirst2020At(5, 30, 0)}, wantTimeUntilNextRun: 3 * time.Hour},
		{name: "job runs every 2 days, just ran at 5:30AM and should be scheduled for 2 days at 8:30AM", job: &Job{interval: 2, unit: days, atTime: 8*time.Hour + 30*time.Minute, lastRun: januaryFirst2020At(5, 30, 0)}, wantTimeUntilNextRun: (2 * day) + 3*time.Hour},
		{name: "job runs every 2 days, just ran at 8:30AM and should be scheduled for 2 days at 8:30AM", job: &Job{interval: 2, unit: days, atTime: 8*time.Hour + 30*time.Minute, lastRun: januaryFirst2020At(8, 30, 0)}, wantTimeUntilNextRun: 2 * day},
		{name: "daily, last run was 1 second ago", job: &Job{interval: 1, unit: days, atTime: 12 * time.Hour, lastRun: ft.Now(time.UTC).Add(-time.Second)}, wantTimeUntilNextRun: 1 * day},
		//// WEEKS
		{name: "every week should run in 7 days", job: &Job{interval: 1, unit: weeks, lastRun: januaryFirst2020At(0, 0, 0)}, wantTimeUntilNextRun: 7 * day},
		{name: "every week with .At time rule should run respect .At time rule", job: &Job{interval: 1, atTime: _getHours(9) + _getMinutes(30), unit: weeks, lastRun: januaryFirst2020At(9, 30, 0)}, wantTimeUntilNextRun: 7 * day},
		{name: "every two weeks at 09:30AM should run in 14 days at 09:30AM", job: &Job{interval: 2, unit: weeks, lastRun: januaryFirst2020At(0, 0, 0)}, wantTimeUntilNextRun: 14 * day},
		{name: "every 31 weeks ran at jan 1st at midnight should run at August 5, 2020", job: &Job{interval: 31, unit: weeks, lastRun: januaryFirst2020At(0, 0, 0)}, wantTimeUntilNextRun: 31 * 7 * day},
		// MONTHS
		{name: "every month in a 31 days month should be scheduled for 31 days ahead", job: &Job{interval: 1, unit: months, lastRun: januaryFirst2020At(0, 0, 0)}, wantTimeUntilNextRun: 31 * day},
		{name: "every month in a 30 days month should be scheduled for 30 days ahead", job: &Job{interval: 1, unit: months, lastRun: time.Date(2020, time.April, 1, 0, 0, 0, 0, time.UTC)}, wantTimeUntilNextRun: 30 * day},
		{name: "every month at february on leap year should count 29 days", job: &Job{interval: 1, unit: months, lastRun: time.Date(2020, time.February, 1, 0, 0, 0, 0, time.UTC)}, wantTimeUntilNextRun: 29 * day},
		{name: "every month at february on non leap year should count 28 days", job: &Job{interval: 1, unit: months, lastRun: time.Date(2019, time.February, 1, 0, 0, 0, 0, time.UTC)}, wantTimeUntilNextRun: 28 * day},
		{name: "every month at first day at time should run next month + at time", job: &Job{interval: 1, unit: months, atTime: _getHours(9) + _getMinutes(30), lastRun: januaryFirst2020At(9, 30, 0)}, wantTimeUntilNextRun: 31*day + _getHours(9) + _getMinutes(30)},
		{name: "every month at day should consider at days", job: &Job{interval: 1, unit: months, daysOfTheMonth: []int{2}, lastRun: januaryFirst2020At(0, 0, 0)}, wantTimeUntilNextRun: 1 * day},
		{name: "every month at day should consider at hours", job: &Job{interval: 1, unit: months, atTime: _getHours(9) + _getMinutes(30), lastRun: januaryFirst2020At(0, 0, 0)}, wantTimeUntilNextRun: 31*day + _getHours(9) + _getMinutes(30)},
		{name: "every month on the first day, but started on january 8th, should run February 1st", job: &Job{interval: 1, unit: months, daysOfTheMonth: []int{1}, lastRun: januaryFirst2020At(0, 0, 0).AddDate(0, 0, 7)}, wantTimeUntilNextRun: 24 * day},
		{name: "every 2 months at day 1, starting at day 1, should run in 2 months", job: &Job{interval: 2, unit: months, daysOfTheMonth: []int{1}, lastRun: januaryFirst2020At(0, 0, 0)}, wantTimeUntilNextRun: 31*day + 29*day},                          // 2020 january and february
		{name: "every 2 months at day 2, starting at day 1, should run in 2 months + 1 day", job: &Job{interval: 2, unit: months, daysOfTheMonth: []int{2}, lastRun: januaryFirst2020At(0, 0, 0)}, wantTimeUntilNextRun: 31*day + 29*day + 1*day},          // 2020 january and february
		{name: "every 2 months at day 1, starting at day 2, should run in 2 months - 1 day", job: &Job{interval: 2, unit: months, daysOfTheMonth: []int{1}, lastRun: januaryFirst2020At(0, 0, 0).AddDate(0, 0, 1)}, wantTimeUntilNextRun: 30*day + 29*day}, // 2020 january and february
		{name: "every 13 months at day 1, starting at day 2 run in 13 months - 1 day", job: &Job{interval: 13, unit: months, daysOfTheMonth: []int{1}, lastRun: januaryFirst2020At(0, 0, 0).AddDate(0, 0, 1)}, wantTimeUntilNextRun: januaryFirst2020At(0, 0, 0).AddDate(0, 13, -1).Sub(januaryFirst2020At(0, 0, 0))},
		//// WEEKDAYS
		{name: "every weekday starting on one day before it should run this weekday", job: &Job{interval: 1, unit: weeks, scheduledWeekdays: []time.Weekday{*_tuesdayWeekday()}, lastRun: mondayAt(0, 0, 0)}, wantTimeUntilNextRun: 1 * day},
		{name: "every weekday starting on same weekday should run on same immediately", job: &Job{interval: 1, unit: weeks, scheduledWeekdays: []time.Weekday{*_tuesdayWeekday()}, lastRun: mondayAt(0, 0, 0).AddDate(0, 0, 1)}, wantTimeUntilNextRun: 0},
		{name: "every 2 weekdays counting this week's weekday should run next weekday", job: &Job{interval: 2, unit: weeks, scheduledWeekdays: []time.Weekday{*_tuesdayWeekday()}, lastRun: mondayAt(0, 0, 0)}, wantTimeUntilNextRun: day},
		{name: "every weekday starting on one day after should count days remaining", job: &Job{interval: 1, unit: weeks, scheduledWeekdays: []time.Weekday{*_tuesdayWeekday()}, lastRun: mondayAt(0, 0, 0).AddDate(0, 0, 2)}, wantTimeUntilNextRun: 6 * day},
		{name: "every weekday starting before jobs .At() time should run at same day at time", job: &Job{interval: 1, unit: weeks, atTime: _getHours(9) + _getMinutes(30), scheduledWeekdays: []time.Weekday{*_tuesdayWeekday()}, lastRun: mondayAt(0, 0, 0).AddDate(0, 0, 1)}, wantTimeUntilNextRun: _getHours(9) + _getMinutes(30)},
		{name: "every weekday starting at same day at time that already passed should run at next week at time", job: &Job{interval: 1, unit: weeks, atTime: _getHours(9) + _getMinutes(30), scheduledWeekdays: []time.Weekday{*_tuesdayWeekday()}, lastRun: mondayAt(10, 30, 0).AddDate(0, 0, 1)}, wantTimeUntilNextRun: 6*day + _getHours(23) + _getMinutes(0)},
	}

	for _, tc := range testCases {
		t.Run(tc.name, func(t *testing.T) {
			s := NewScheduler(time.UTC)
			s.time = ft
			got := s.durationToNextRun(tc.job.LastRun(), tc.job).duration
			assert.Equalf(t, tc.wantTimeUntilNextRun, got, fmt.Sprintf("expected %s / got %s", tc.wantTimeUntilNextRun.String(), got.String()))
		})
	}
}

// helper test method
func _tuesdayWeekday() *time.Weekday {
	tuesday := time.Tuesday
	return &tuesday
}

// helper test method
func _getSeconds(i int) time.Duration {
	return time.Duration(i) * time.Second
}

// helper test method
func _getHours(i int) time.Duration {
	return time.Duration(i) * time.Hour
}

// helper test method
func _getMinutes(i int) time.Duration {
	return time.Duration(i) * time.Minute
}

func TestScheduler_Do(t *testing.T) {
	var testCases = []struct {
		description string
		evalFunc    func(*Scheduler)
	}{
		{
			"adding a new job before scheduler starts does not schedule job",
			func(s *Scheduler) {
				s.setRunning(false)
				job, err := s.Every(1).Second().Do(func() {})
				assert.Equal(t, nil, err)
				assert.True(t, job.NextRun().IsZero())
			},
		},
		{
			"adding a new job when scheduler is running schedules job",
			func(s *Scheduler) {
				s.setRunning(true)
				job, err := s.Every(1).Second().Do(func() {})
				assert.Equal(t, nil, err)
				assert.False(t, job.NextRun().IsZero())
			},
		},
		{
			description: "error due to the arg passed to Do() not being a function",
			evalFunc: func(s *Scheduler) {
				_, err := s.Every(1).Second().Do(1)
				assert.EqualError(t, err, ErrNotAFunction.Error())
				assert.Zero(t, s.Len(), "The job should be deleted if the arg passed to Do() is not a function")
			},
		},
		{
			description: "positive case",
			evalFunc: func(s *Scheduler) {
				_, err := s.Every(1).Day().Do(func() {})
				require.NoError(t, err)
				assert.Equal(t, 1, s.Len())
			},
		},
	}
	for _, tc := range testCases {
		t.Run(tc.description, func(t *testing.T) {
			s := NewScheduler(time.Local)
			tc.evalFunc(s)
		})
	}
}

func TestRunJobsWithLimit(t *testing.T) {
	t.Run("simple", func(t *testing.T) {
		semaphore := make(chan bool)

		s := NewScheduler(time.UTC)

		j, err := s.Every("100ms").Do(func() {
			semaphore <- true
		})
		require.NoError(t, err)
		j.LimitRunsTo(1)

		s.StartAsync()
		time.Sleep(200 * time.Millisecond)

		var counter int
		now := time.Now()
		for time.Now().Before(now.Add(200 * time.Millisecond)) {
			select {
			case <-semaphore:
				counter++
			default:
			}
		}

		assert.Equal(t, 1, counter)
	})

	t.Run("remove after last run", func(t *testing.T) {
		semaphore := make(chan bool)

		s := NewScheduler(time.UTC)

		j, err := s.Every("100ms").Do(func() {
			semaphore <- true
		})
		require.NoError(t, err)
		j.LimitRunsTo(1)

		s.StartAsync()
		time.Sleep(200 * time.Millisecond)

		var counter int
		select {
		case <-time.After(200 * time.Millisecond):
			assert.Equal(t, 0, s.Len())
		case <-semaphore:
			counter++
			require.LessOrEqual(t, counter, 1)
		}
	})

	t.Run("remove unique tags also", func(t *testing.T) {
		semaphore := make(chan bool)

		s := NewScheduler(time.UTC)
		s.TagsUnique()

		j, err := s.Every("100ms").Tag("tag1", "tag2", "tag3").Do(func() {
			semaphore <- true
		})
		require.NoError(t, err)
		j.LimitRunsTo(1)

		s.StartAsync()
		time.Sleep(200 * time.Millisecond)

		var counter int
		select {
		case <-time.After(200 * time.Millisecond):
			assert.Equal(t, 0, s.Len())
		case <-semaphore:
			counter++
			require.LessOrEqual(t, counter, 1)
		}

		s.tags.Range(func(key, value interface{}) bool {
			assert.FailNow(t, "map should be empty")
			return true
		})
	})
}

func TestCalculateMonthsError(t *testing.T) {
	testCases := []struct {
		desc       string
		dayOfMonth int
	}{
		{"invalid -1", -1},
		{"invalid 29", 29},
	}

	for _, tc := range testCases {
		t.Run(tc.desc, func(t *testing.T) {
			s := NewScheduler(time.UTC)
			job, err := s.Every(1).Month(tc.dayOfMonth).Do(func() {
				fmt.Println("hello task")
			})
			require.Error(t, err)
			require.Nil(t, job)
		})
	}
}

func TestCalculateMonths(t *testing.T) {
	maySecond2021At0200 := time.Date(2021, 5, 2, 2, 0, 0, 0, time.UTC)

	maySecond2021At0800 := time.Date(2021, 5, 2, 8, 0, 0, 0, time.UTC)

	maySixth2021At0200 := time.Date(2021, 5, 6, 2, 0, 0, 0, time.UTC)

	maySixth2021At0500 := fakeTime{onNow: func(l *time.Location) time.Time {
		return time.Date(2021, 5, 6, 5, 0, 0, 0, l)
	}}

	maySixth2021At0800 := time.Date(2021, 5, 6, 8, 0, 0, 0, time.UTC)

	mayTenth2021At0200 := time.Date(2021, 5, 10, 2, 0, 0, 0, time.UTC)

	mayTenth2021At0800 := time.Date(2021, 5, 10, 8, 0, 0, 0, time.UTC)

	day := time.Hour * 24

	testCases := []struct {
		description          string
		job                  *Job
		wantTimeUntilNextRun time.Duration
	}{
		{description: "day before current and before current time, should run next month", job: &Job{interval: 1, unit: months, daysOfTheMonth: []int{2}, atTime: _getHours(2), lastRun: maySixth2021At0500.Now(time.UTC)}, wantTimeUntilNextRun: (31 * day) - maySixth2021At0500.Now(time.UTC).Sub(maySecond2021At0200)},
		{description: "day before current and after current time, should run next month", job: &Job{interval: 1, unit: months, daysOfTheMonth: []int{2}, atTime: _getHours(8), lastRun: maySixth2021At0500.Now(time.UTC)}, wantTimeUntilNextRun: (31 * day) - maySixth2021At0500.Now(time.UTC).Sub(maySecond2021At0800)},
		{description: "current day and before current time, should run next month", job: &Job{interval: 1, unit: months, daysOfTheMonth: []int{6}, atTime: _getHours(2), lastRun: maySixth2021At0500.Now(time.UTC)}, wantTimeUntilNextRun: (31 * day) - maySixth2021At0500.Now(time.UTC).Sub(maySixth2021At0200)},
		{description: "current day and after current time, should run on current day", job: &Job{interval: 1, unit: months, daysOfTheMonth: []int{6}, atTime: _getHours(8), lastRun: maySixth2021At0500.Now(time.UTC)}, wantTimeUntilNextRun: maySixth2021At0800.Sub(maySixth2021At0500.Now(time.UTC))},
		{description: "day after current and before current time, should run on current month", job: &Job{interval: 1, unit: months, daysOfTheMonth: []int{10}, atTime: _getHours(2), lastRun: maySixth2021At0500.Now(time.UTC)}, wantTimeUntilNextRun: mayTenth2021At0200.Sub(maySixth2021At0500.Now(time.UTC))},
		{description: "day after current and after current time, should run on current month", job: &Job{interval: 1, unit: months, daysOfTheMonth: []int{10}, atTime: _getHours(8), lastRun: maySixth2021At0500.Now(time.UTC)}, wantTimeUntilNextRun: mayTenth2021At0800.Sub(maySixth2021At0500.Now(time.UTC))},
	}

	for _, tc := range testCases {
		t.Run(tc.description, func(t *testing.T) {
			s := NewScheduler(time.UTC)
			s.time = maySixth2021At0500
			got := s.durationToNextRun(tc.job.LastRun(), tc.job).duration
			assert.Equalf(t, tc.wantTimeUntilNextRun, got, fmt.Sprintf("expected %s / got %s", tc.wantTimeUntilNextRun.String(), got.String()))
		})
	}
}

func TestScheduler_SingletonMode(t *testing.T) {

	testCases := []struct {
		description string
		removeJob   bool
	}{
		{"with scheduler stop", false},
		{"with job removal", true},
	}

	for _, tc := range testCases {
		t.Run(tc.description, func(t *testing.T) {

			s := NewScheduler(time.UTC)
			var trigger int32

			j, err := s.Every("100ms").SingletonMode().Do(func() {
				if atomic.LoadInt32(&trigger) == 1 {
					t.Fatal("Restart should not occur")
				}
				atomic.AddInt32(&trigger, 1)
				time.Sleep(300 * time.Millisecond)
			})
			require.NoError(t, err)

			s.StartAsync()
			time.Sleep(200 * time.Millisecond)

			if tc.removeJob {
				s.RemoveByReference(j)
				time.Sleep(300 * time.Millisecond)
			}
			s.Stop()
		})
	}

}

func TestScheduler_LimitRunsTo(t *testing.T) {
	t.Run("job added before starting scheduler", func(t *testing.T) {
		semaphore := make(chan bool)

		s := NewScheduler(time.UTC)

		_, err := s.Every("100ms").LimitRunsTo(1).Do(func() {
			semaphore <- true
		})
		require.NoError(t, err)

		s.StartAsync()
		time.Sleep(200 * time.Millisecond)

		var counter int
		select {
		case <-time.After(200 * time.Millisecond):
			assert.Equal(t, 1, counter)
		case <-semaphore:
			counter++
			require.LessOrEqual(t, counter, 1)
		}
	})

	t.Run("job added after starting scheduler", func(t *testing.T) {
		semaphore := make(chan bool)

		s := NewScheduler(time.UTC)
		s.StartAsync()

		_, err := s.Every("100ms").LimitRunsTo(1).Do(func() {
			semaphore <- true
		})
		require.NoError(t, err)

		time.Sleep(200 * time.Millisecond)

		var counter int
		select {
		case <-time.After(200 * time.Millisecond):
			assert.Equal(t, 1, counter)
		case <-semaphore:
			counter++
			require.LessOrEqual(t, counter, 1)
		}
	})

	t.Run("job added after starting scheduler - using job's LimitRunsTo - results in two runs", func(t *testing.T) {
		semaphore := make(chan bool)

		s := NewScheduler(time.UTC)
		s.StartAsync()

		j, err := s.Every("100ms").Do(func() {
			semaphore <- true
		})
		require.NoError(t, err)
		j.LimitRunsTo(1)

		time.Sleep(200 * time.Millisecond)

		var counter int
		select {
		case <-time.After(200 * time.Millisecond):
			assert.Equal(t, 2, counter)
		case <-semaphore:
			counter++
			require.LessOrEqual(t, counter, 2)
		}
	})
}

func TestScheduler_SetMaxConcurrentJobs(t *testing.T) {
	semaphore := make(chan bool)

	testCases := []struct {
		description       string
		maxConcurrentJobs int
		mode              limitMode
		expectedRuns      int
		removeJobs        bool
		f                 func()
	}{
		// Expecting a total of 4 job runs:
		// 0s - jobs 1 & 3 run, job 2 hits the limit and is skipped
		// 1s - job 1 hits the limit and is skipped
		// 2s - job 1 & 2 run
		// 3s - job 1 hits the limit and is skipped
		{"reschedule mode", 2, RescheduleMode, 4, false,
			func() {
				semaphore <- true
				time.Sleep(200 * time.Millisecond)
			},
		},

		// Expecting a total of 8 job runs. The exact order of jobs may vary, for example:
		// 0s - jobs 2 & 3 run, job 1 hits the limit and waits
		// 1s - job 1 runs twice, the blocked run and the regularly scheduled run
		// 2s - jobs 1 & 3 run
		// 3s - jobs 2 & 3 run, job 1 hits the limit and waits
		{"wait mode", 2, WaitMode, 8, false,
			func() {
				semaphore <- true
				time.Sleep(100 * time.Millisecond)
			},
		},

		// Same as above - this confirms the same behavior when jobs are removed rather than the scheduler being stopped
		{"wait mode - with job removal", 2, WaitMode, 8, true,
			func() {
				semaphore <- true
				time.Sleep(100 * time.Millisecond)
			},
		},
	}

	for _, tc := range testCases {
		t.Run(tc.description, func(t *testing.T) {

			s := NewScheduler(time.UTC)
			s.SetMaxConcurrentJobs(tc.maxConcurrentJobs, tc.mode)

			j1, err := s.Every("100ms").Do(tc.f)
			require.NoError(t, err)

			j2, err := s.Every("200ms").Do(tc.f)
			require.NoError(t, err)

			j3, err := s.Every("300ms").Do(tc.f)
			require.NoError(t, err)

			s.StartAsync()

			var counter int

			now := time.Now()
			for time.Now().Before(now.Add(400 * time.Millisecond)) {
				select {
				case <-semaphore:
					counter++
				default:
				}
			}

			if tc.removeJobs {
				s.RemoveByReference(j1)
				s.RemoveByReference(j2)
				s.RemoveByReference(j3)
				defer s.Stop()
			} else {
				s.Stop()
			}

			// make sure no more jobs are run as the executor
			// or job should be properly stopped

			now = time.Now()
			for time.Now().Before(now.Add(200 * time.Millisecond)) {
				select {
				case <-semaphore:
					counter++
				default:
				}
			}

			assert.Equal(t, tc.expectedRuns, counter)
		})
	}
}

func TestScheduler_TagsUnique(t *testing.T) {
	const (
		foo = "foo"
		bar = "bar"
		baz = "baz"
	)

	s := NewScheduler(time.UTC)
	s.TagsUnique()

	j, err := s.Every("1s").Tag(foo, bar).Do(func() {})
	require.NoError(t, err)

	// uniqueness not enforced on jobs tagged with job.Tag()
	// thus tagging the job here is allowed
	j.Tag(baz)
	_, err = s.Every("1s").Tag(baz).Do(func() {})
	require.NoError(t, err)

	_, err = s.Every("1s").Tag(foo).Do(func() {})
	assert.EqualError(t, err, ErrTagsUnique(foo).Error())

	_, err = s.Every("1s").Tag(bar).Do(func() {})
	assert.EqualError(t, err, ErrTagsUnique(bar).Error())

}

func TestScheduler_DoParameterValidation(t *testing.T) {
	testCases := []struct {
		description string
		parameters  []interface{}
	}{
		{"less than expected", []interface{}{"p1"}},
		{"more than expected", []interface{}{"p1", "p2", "p3"}},
	}

	for _, tc := range testCases {
		t.Run(tc.description, func(t *testing.T) {
			s := NewScheduler(time.UTC)
			f := func(s1, s2 string) {
				fmt.Println("ok")
			}

			_, err := s.Every(1).Days().StartAt(time.Now().UTC().Add(time.Second*10)).Do(f, tc.parameters...)
			assert.EqualError(t, err, ErrWrongParams.Error())
		})
	}
}

func TestScheduler_Job(t *testing.T) {
	s := NewScheduler(time.UTC)

	j1, err := s.Every("1s").Do(func() { log.Println("one") })
	require.NoError(t, err)
	assert.Equal(t, j1, s.getCurrentJob())

	j2, err := s.Every("1s").Do(func() { log.Println("two") })
	require.NoError(t, err)
	assert.Equal(t, j2, s.getCurrentJob())

	s.Job(j1)
	assert.Equal(t, j1, s.getCurrentJob())

	s.Job(j2)
	assert.Equal(t, j2, s.getCurrentJob())
}

func TestScheduler_Update(t *testing.T) {
	t.Run("happy path", func(t *testing.T) {
		s := NewScheduler(time.UTC)

		var counterMutex sync.RWMutex
		counter := 0

		j, err := s.Every(1).Day().Do(func() { counterMutex.Lock(); defer counterMutex.Unlock(); counter++ })
		require.NoError(t, err)

		s.StartAsync()

		time.Sleep(300 * time.Millisecond)
		_, err = s.Job(j).Every("500ms").Update()
		require.NoError(t, err)

		time.Sleep(550 * time.Millisecond)
		_, err = s.Job(j).Every("750ms").Update()
		require.NoError(t, err)

		time.Sleep(800 * time.Millisecond)
		_, err = s.Job(j).CronWithSeconds("*/1 * * * * *").Update()
		require.NoError(t, err)

		time.Sleep(time.Second)
		s.Stop()

		counterMutex.RLock()
		defer counterMutex.RUnlock()
		assert.Equal(t, 4, counter)
	})

	t.Run("happy singleton mode", func(t *testing.T) {
		s := NewScheduler(time.UTC)

		var counterMutex sync.RWMutex
		counter := 0

		j, err := s.Every(1).Day().SingletonMode().Do(func() { counterMutex.Lock(); defer counterMutex.Unlock(); counter++ })
		require.NoError(t, err)

		s.StartAsync()

		time.Sleep(300 * time.Millisecond)
		_, err = s.Job(j).Every("500ms").Update()
		require.NoError(t, err)

		time.Sleep(550 * time.Millisecond)
		_, err = s.Job(j).Every("750ms").Update()
		require.NoError(t, err)

		time.Sleep(800 * time.Millisecond)
		s.Stop()

		counterMutex.RLock()
		defer counterMutex.RUnlock()
		assert.Equal(t, 3, counter)
	})

	t.Run("update called without job call", func(t *testing.T) {
		s := NewScheduler(time.UTC)
		_, err := s.Every("1s").Do(func() {})
		require.NoError(t, err)

		_, err = s.Update()
		assert.EqualError(t, err, ErrUpdateCalledWithoutJob.Error())
	})

	t.Run("update, delete, create", func(t *testing.T) {
		s := NewScheduler(time.UTC)

		var counterMutex sync.RWMutex
		counter := 0

		j, err := s.Every(1).Day().Do(func() { counterMutex.Lock(); defer counterMutex.Unlock(); counter++ })
		require.NoError(t, err)

		s.StartAsync()

		time.Sleep(300 * time.Millisecond)
		_, err = s.Job(j).Every("500ms").Update()
		require.NoError(t, err)

		time.Sleep(550 * time.Millisecond)
		s.RemoveByReference(j)

		j, err = s.Every("750ms").WaitForSchedule().Do(func() { counterMutex.Lock(); defer counterMutex.Unlock(); counter++ })
		require.NoError(t, err)

		time.Sleep(800 * time.Millisecond)
		_, err = s.Job(j).CronWithSeconds("*/1 * * * * *").Update()
		require.NoError(t, err)

		time.Sleep(time.Second)
		s.Stop()

		counterMutex.RLock()
		defer counterMutex.RUnlock()
		assert.Equal(t, 4, counter)
	})
}

func TestScheduler_RunByTag(t *testing.T) {
	var (
		s     = NewScheduler(time.Local)
		count = 0
		wg    sync.WaitGroup
	)

	s.Every(1).Day().StartAt(time.Now().Add(time.Hour)).Tag("tag").Do(func() {
		count++
		wg.Done()
	})
	wg.Add(1)
	s.StartAsync()
	assert.NoError(t, s.RunByTag("tag"))

	wg.Wait()
	assert.Equal(t, 1, count)
	assert.Error(t, s.RunByTag("wrong-tag"))
}

func TestScheduler_Cron(t *testing.T) {
	ft := fakeTime{onNow: func(l *time.Location) time.Time {
		// January 1st, 12 noon, Thursday, 1970
		return time.Date(1970, 1, 1, 12, 0, 0, 0, l)
	}}

	s := NewScheduler(time.UTC)
	s.time = ft

	testCases := []struct {
		description     string
		cronTab         string
		expectedNextRun time.Time
		expectedError   error
	}{
		// https://crontab.guru/
		{"every minute", "*/1 * * * *", ft.onNow(time.UTC).Add(1 * time.Minute), nil},
		{"every day 1am", "0 1 * * *", ft.onNow(time.UTC).Add(13 * time.Hour), nil},
		{"weekends only", "0 0 * * 6,0", ft.onNow(time.UTC).Add(36 * time.Hour), nil},
		{"at time monday thru friday", "0 22 * * 1-5", ft.onNow(time.UTC).Add(10 * time.Hour), nil},
		{"every minute in range, monday thru friday", "15-30 * * * 1-5", ft.onNow(time.UTC).Add(15 * time.Minute), nil},
		{"at every minute past every hour from 1 through 5 on every day-of-week from Monday through Friday.", "* 1-5 * * 1-5", ft.onNow(time.UTC).Add(13 * time.Hour), nil},
		{"hourly", "@hourly", ft.onNow(time.UTC).Add(1 * time.Hour), nil},
		{"bad expression", "bad", time.Time{}, wrapOrError(fmt.Errorf("expected exactly 5 fields, found 1: [bad]"), ErrCronParseFailure)},
	}

	for _, tc := range testCases {
		t.Run(tc.description, func(t *testing.T) {
			j, err := s.Cron(tc.cronTab).Do(func() {})
			if tc.expectedError == nil {
				require.NoError(t, err)

				s.scheduleNextRun(j)

				assert.Exactly(t, tc.expectedNextRun, j.NextRun())
			} else {
				assert.EqualError(t, err, tc.expectedError.Error())
			}
		})
	}

	t.Run("error At() called with Cron()", func(t *testing.T) {
		_, err := s.Cron("@hourly").At("1:00").Do(func() {})
		assert.EqualError(t, err, ErrAtTimeNotSupported.Error())
	})

	t.Run("error Weekday() called with Cron()", func(t *testing.T) {
		_, err := s.Cron("@hourly").Sunday().Do(func() {})
		assert.EqualError(t, err, wrapOrError(ErrInvalidIntervalUnitsSelection, ErrWeekdayNotSupported).Error())
	})
}

func TestScheduler_CronWithSeconds(t *testing.T) {
	ft := fakeTime{onNow: func(l *time.Location) time.Time {
		// January 1st, 12 noon, Thursday, 1970
		return time.Date(1970, 1, 1, 12, 0, 0, 0, l)
	}}

	s := NewScheduler(time.UTC)
	s.time = ft

	testCases := []struct {
		description     string
		cronTab         string
		expectedNextRun time.Time
		expectedError   error
	}{
		// https://crontab.guru/
		{"every second", "*/1 * * * * *", ft.onNow(time.UTC).Add(1 * time.Second), nil},
		{"every second from 0-30", "0-30 * * * * *", ft.onNow(time.UTC).Add(1 * time.Second), nil},
		{"every minute", "0 */1 * * * *", ft.onNow(time.UTC).Add(1 * time.Minute), nil},
		{"every day 1am", "* 0 1 * * *", ft.onNow(time.UTC).Add(13 * time.Hour), nil},
		{"weekends only", "* 0 0 * * 6,0", ft.onNow(time.UTC).Add(36 * time.Hour), nil},
		{"at time monday thru friday", "* 0 22 * * 1-5", ft.onNow(time.UTC).Add(10 * time.Hour), nil},
		{"every minute in range, monday thru friday", "* 15-30 * * * 1-5", ft.onNow(time.UTC).Add(15 * time.Minute), nil},
		{"at every minute past every hour from 1 through 5 on every day-of-week from Monday through Friday.", "* * 1-5 * * 1-5", ft.onNow(time.UTC).Add(13 * time.Hour), nil},
		{"hourly", "@hourly", ft.onNow(time.UTC).Add(1 * time.Hour), nil},
		{"bad expression", "bad", time.Time{}, wrapOrError(fmt.Errorf("expected exactly 6 fields, found 1: [bad]"), ErrCronParseFailure)},
	}

	for _, tc := range testCases {
		t.Run(tc.description, func(t *testing.T) {
			j, err := s.CronWithSeconds(tc.cronTab).Do(func() {})
			if tc.expectedError == nil {
				require.NoError(t, err)

				s.scheduleNextRun(j)

				assert.Exactly(t, tc.expectedNextRun, j.NextRun())
			} else {
				assert.EqualError(t, err, tc.expectedError.Error())
			}
		})
	}

	t.Run("error At() called with Cron()", func(t *testing.T) {
		_, err := s.Cron("@hourly").At("1:00").Do(func() {})
		assert.EqualError(t, err, ErrAtTimeNotSupported.Error())
	})

	t.Run("error Weekday() called with Cron()", func(t *testing.T) {
		_, err := s.Cron("@hourly").Sunday().Do(func() {})
		assert.EqualError(t, err, wrapOrError(ErrInvalidIntervalUnitsSelection, ErrWeekdayNotSupported).Error())
	})
}

func TestScheduler_WaitForSchedule(t *testing.T) {
	s := NewScheduler(time.UTC)

	var counterMutex sync.RWMutex
	counter := 0

	_, err := s.Every("100ms").WaitForSchedule().Do(func() { counterMutex.Lock(); defer counterMutex.Unlock(); counter++ })
	require.NoError(t, err)
	s.StartAsync()

	time.Sleep(350 * time.Millisecond)
	s.Stop()

	counterMutex.RLock()
	defer counterMutex.RUnlock()
	assert.Equal(t, 3, counter)
}

func TestScheduler_WaitForSchedules(t *testing.T) {
	s := NewScheduler(time.UTC)
	s.WaitForScheduleAll()

	var counterMutex sync.RWMutex
	counter := 0

	_, err := s.Every("1s").Do(func() { counterMutex.Lock(); defer counterMutex.Unlock(); counter++; log.Println("job 1") })
	require.NoError(t, err)

	_, err = s.CronWithSeconds("*/1 * * * * *").Do(func() { counterMutex.Lock(); defer counterMutex.Unlock(); counter++; log.Println("job 2") })
	require.NoError(t, err)
	s.StartAsync()

	time.Sleep(1100 * time.Millisecond)
	s.Stop()

	counterMutex.RLock()
	defer counterMutex.RUnlock()
	assert.Equal(t, 2, counter)
}

func TestScheduler_LenWeekDays(t *testing.T) {

	testCases := []struct {
		description string
		weekDays    []time.Weekday
		finalLen    int
	}{
		{"no week day", []time.Weekday{}, 0},
		{"equal week day", []time.Weekday{time.Friday, time.Friday, time.Friday}, 1},
		{"more than one week day", []time.Weekday{time.Friday, time.Saturday, time.Sunday}, 3},
	}

	for _, tc := range testCases {
		t.Run(tc.description, func(t *testing.T) {
			s := NewScheduler(time.UTC)
			s = s.Every(1)
			for _, weekDay := range tc.weekDays {
				s = s.Weekday(weekDay)
			}
			j, err := s.Do(func() {})
			require.NoError(t, err)
			assert.Equal(t, len(j.scheduledWeekdays), tc.finalLen)
		})
	}

}

func TestScheduler_CallNextWeekDay(t *testing.T) {
	januaryFirst2020At := func(hour, minute, second int) time.Time {
		return time.Date(2020, time.January, 1, hour, minute, second, 0, time.UTC)
	}

	const wantTimeUntilNextRun = time.Hour * 24 * 2
	var lastRun = januaryFirst2020At(0, 0, 0)

	testCases := []struct {
		description string
		weekDays    []time.Weekday
	}{
		{"week days not in order", []time.Weekday{time.Monday, time.Friday}},
		{"week days in order", []time.Weekday{time.Friday, time.Monday}},
	}

	for _, tc := range testCases {
		t.Run(tc.description, func(t *testing.T) {

			s := NewScheduler(time.UTC)
			s.Every(1)

			for _, weekDay := range tc.weekDays {
				s.Weekday(weekDay)
			}

			job, err := s.Do(func() {})
			require.NoError(t, err)
			job.lastRun = lastRun

			got := s.durationToNextRun(lastRun, job).duration
			assert.Equal(t, wantTimeUntilNextRun, got)

		})
	}

}

func TestScheduler_CheckNextWeekDay(t *testing.T) {
	januaryFirst2020At := func(hour, minute, second int) time.Time {
		return time.Date(2020, time.January, 1, hour, minute, second, 0, time.UTC)
	}
	januarySecond2020At := func(hour, minute, second int) time.Time {
		return time.Date(2020, time.January, 2, hour, minute, second, 0, time.UTC)
	}
	const (
		wantTimeUntilNextFirstRun = 1 * time.Second
		// all day long
		wantTimeUntilNextSecondRun = 24 * time.Hour
	)

	t.Run("check slice next run", func(t *testing.T) {
		s := NewScheduler(time.UTC)
		lastRun := januaryFirst2020At(23, 59, 59)
		secondLastRun := januarySecond2020At(0, 0, 0)

		job, err := s.Every(1).Week().Friday().Thursday().Do(func() {})
		require.NoError(t, err)
		job.lastRun = lastRun

		gotFirst := s.durationToNextRun(lastRun, job).duration
		assert.Equal(t, wantTimeUntilNextFirstRun, gotFirst)

		job.lastRun = secondLastRun
		gotSecond := s.durationToNextRun(secondLastRun, job).duration
		assert.Equal(t, wantTimeUntilNextSecondRun, gotSecond)

	})
}

func TestScheduler_CheckEveryWeekHigherThanOne(t *testing.T) {
	januaryDay2020At := func(day int) time.Time {
		return time.Date(2020, time.January, day, 0, 0, 0, 0, time.UTC)
	}

	testCases := []struct {
		description string
		interval    int
		weekDays    []time.Weekday
		daysToTest  []int
		caseTest    int
	}{
		{description: "every two weeks after run the first scheduled task", interval: 2, weekDays: []time.Weekday{time.Thursday}, daysToTest: []int{1, 2}, caseTest: 1},
		{description: "every three weeks after run the first scheduled task", interval: 3, weekDays: []time.Weekday{time.Thursday}, daysToTest: []int{1, 2}, caseTest: 2},
		{description: "every two weeks after run the first 2 scheduled tasks", interval: 2, weekDays: []time.Weekday{time.Thursday, time.Friday}, daysToTest: []int{1, 2, 3}, caseTest: 3},
	}

	const (
		wantTimeUntilNextRunOneDay = 24 * time.Hour
		// two weeks difference
		wantTimeUntilNextRunTwoWeeks = 24 * time.Hour * 14
		// three weeks difference
		wantTimeUntilNextRunThreeWeeks = 24 * time.Hour * 21
		// two weeks difference less one day
		wantTimeUntilNextRunTwoWeeksLessOneDay = 24 * time.Hour * (14 - 1)
	)

	for _, tc := range testCases {
		t.Run(tc.description, func(t *testing.T) {
			s := NewScheduler(time.UTC)
			s.Every(tc.interval)

			for _, weekDay := range tc.weekDays {
				s.Weekday(weekDay)
			}
			job, err := s.Do(func() {})
			require.NoError(t, err)
			for numJob, day := range tc.daysToTest {
				lastRun := januaryDay2020At(day)

				job.lastRun = lastRun
				got := s.durationToNextRun(lastRun, job).duration

				if numJob < len(tc.weekDays) {
					assert.Equal(t, wantTimeUntilNextRunOneDay, got)
				} else {
					if tc.caseTest == 1 {
						assert.Equal(t, wantTimeUntilNextRunTwoWeeks, got)
					} else if tc.caseTest == 2 {
						assert.Equal(t, wantTimeUntilNextRunThreeWeeks, got)
					} else if tc.caseTest == 3 {
						assert.Equal(t, wantTimeUntilNextRunTwoWeeksLessOneDay, got)
					}

				}
				job.runCount++
			}

		})
	}

}

func TestScheduler_StartImmediately(t *testing.T) {

	testCases := []struct {
		description                string
		scheduler                  *Scheduler
		expectedToStartImmediately bool
	}{
		{"true cron", NewScheduler(time.UTC).Cron("0 0 * * 6,0").StartImmediately(), true},
		{"true default", NewScheduler(time.UTC).Every("1m"), true},
		{"true every", NewScheduler(time.UTC).Every("1m").StartImmediately(), true},
		{"false cron default", NewScheduler(time.UTC).Cron("0 0 * * 6,0"), false},
	}

	for _, tc := range testCases {
		t.Run(tc.description, func(t *testing.T) {
			j, err := tc.scheduler.Do(func() {})
			require.NoError(t, err)

			assert.Exactly(t, tc.expectedToStartImmediately, j.startsImmediately)
		})
	}
}

func TestScheduler_CheckCalculateDaysOfMonth(t *testing.T) {
	lastRunFirstCaseDate := time.Date(2021, 9, 10, 0, 0, 0, 0, time.UTC)
	lastRunSecondCaseDate := time.Date(2021, 9, 10, 5, 0, 0, 0, time.UTC)
	lastRunThirdCaseDate := time.Date(2021, 10, 6, 0, 0, 0, 0, time.UTC)
	lastRunFourthCaseDate := time.Date(2021, 9, 11, 0, 0, 0, 0, time.UTC)

	curTime := fakeTime{onNow: func(l *time.Location) time.Time {
		return time.Date(2021, 9, 8, 0, 0, 0, 0, l)
	}}

	testCases := []struct {
		description          string
		job                  *Job
		wantTimeUntilNextRun time.Duration
	}{
		{description: "should run current month 10", job: &Job{interval: 1, unit: months, daysOfTheMonth: []int{10, 6}, atTime: _getHours(0), lastRun: curTime.Now(time.UTC)}, wantTimeUntilNextRun: lastRunFirstCaseDate.Sub(curTime.Now(time.UTC))},
		{description: "should run current month 10", job: &Job{interval: 1, unit: months, daysOfTheMonth: []int{10, 6}, atTime: _getHours(5), lastRun: curTime.Now(time.UTC)}, wantTimeUntilNextRun: lastRunSecondCaseDate.Sub(curTime.Now(time.UTC))},
		{description: "should run next month 6", job: &Job{interval: 1, unit: months, daysOfTheMonth: []int{6, 7}, atTime: _getHours(0), lastRun: curTime.Now(time.UTC)}, wantTimeUntilNextRun: lastRunThirdCaseDate.Sub(curTime.Now(time.UTC))},
		{description: "should run next month 11", job: &Job{interval: 1, unit: months, daysOfTheMonth: []int{12, 11}, atTime: _getHours(0), lastRun: curTime.Now(time.UTC)}, wantTimeUntilNextRun: lastRunFourthCaseDate.Sub(curTime.Now(time.UTC))},
	}

	for _, tc := range testCases {
		t.Run(tc.description, func(t *testing.T) {
			s := NewScheduler(time.UTC)
			s.time = curTime
			got := s.durationToNextRun(tc.job.LastRun(), tc.job).duration
			assert.Equalf(t, tc.wantTimeUntilNextRun, got, fmt.Sprintf("expected %s / got %s", tc.wantTimeUntilNextRun.String(), got.String()))
		})
	}
}

func TestScheduler_CheckSetBehaviourBeforeJobCreated(t *testing.T) {
	s := NewScheduler(time.UTC)
	s.Month(1, 2).Every(1).Do(func() {})

}