only remove past if >1, sort next scheduled

job_test.go

@@ -501,12 +501,12 @@ func TestJob_NextRun(t *testing.T) {
 	// run a job every 10 milliseconds that starts 10 milliseconds after the current time
 	j, err := s.NewJob(
 		DurationJob(
-			10*time.Millisecond,
+			100*time.Millisecond,
 		),
 		NewTask(
 			func() {},
 		),
-		WithStartAt(WithStartDateTime(testTime.Add(10*time.Millisecond))),
+		WithStartAt(WithStartDateTime(testTime.Add(100*time.Millisecond))),
 		WithSingletonMode(LimitModeReschedule),
 	)
 	require.NoError(t, err)
@@ -515,18 +515,15 @@ func TestJob_NextRun(t *testing.T) {
 	nextRun, err := j.NextRun()
 	require.NoError(t, err)
 
-	// `NextRun` should report `testTime.Add(10*time.Millisecond)`
-	assert.Equal(t, testTime.Add(10*time.Millisecond), nextRun)
+	assert.Equal(t, testTime.Add(100*time.Millisecond), nextRun)
 
-	// sleep for 11ms to wait for the next job
-	time.Sleep(11 * time.Millisecond)
+	time.Sleep(150 * time.Millisecond)
 
 	nextRun, err = j.NextRun()
 	assert.NoError(t, err)
 
-	// `NextRun` should report a time 20 milliseconds after `testTime`, but instead reports a value that is `30ms` after
-	assert.Equal(t, testTime.Add(20*time.Millisecond), nextRun)
-	assert.Equal(t, 20*time.Millisecond, nextRun.Sub(testTime))
+	assert.Equal(t, testTime.Add(200*time.Millisecond), nextRun)
+	assert.Equal(t, 200*time.Millisecond, nextRun.Sub(testTime))
 
 	err = s.Shutdown()
 	require.NoError(t, err)

scheduler.go

@@ -302,6 +302,9 @@ func (s *scheduler) selectExecJobsOutForRescheduling(id uuid.UUID) {
 		// always grab the last element in the slice as that is the furthest
 		// out in the future and the time from which we want to calculate
 		// the subsequent next run time.
+		slices.SortStableFunc(j.nextScheduled, func(a, b time.Time) int {
+			return a.Compare(b)
+		})
 		j.lastScheduledRun = j.nextScheduled[len(j.nextScheduled)-1]
 	}
 
@@ -345,14 +348,18 @@ func (s *scheduler) selectExecJobsOutCompleted(id uuid.UUID) {
 		return
 	}
 
-	var newNextScheduled []time.Time
-	for _, t := range j.nextScheduled {
-		if t.Before(s.now()) {
-			continue
+	// if the job has more than one nextScheduled time,
+	// we need to remove any that are in the past.
+	if len(j.nextScheduled) > 1 {
+		var newNextScheduled []time.Time
+		for _, t := range j.nextScheduled {
+			if t.Before(s.now()) {
+				continue
+			}
+			newNextScheduled = append(newNextScheduled, t)
 		}
-		newNextScheduled = append(newNextScheduled, t)
+		j.nextScheduled = newNextScheduled
 	}
-	j.nextScheduled = newNextScheduled
 
 	// if the job has a limited number of runs set, we need to
 	// check how many runs have occurred and stop running this

scheduler_test.go

@@ -1622,7 +1622,7 @@ func TestScheduler_RunJobNow(t *testing.T) {
 				WithSingletonMode(LimitModeReschedule),
 			},
 			func() time.Duration {
-				return 20 * time.Second
+				return 10 * time.Second
 			},
 			1,
 		},