Fix implementation of the StopTask method

pkg/scheduler/scheduler.go

@@ -199,22 +199,26 @@ func (scheduler *Scheduler) ScheduleTask(name string, startTime *time.Time, dura
 }
 
 // StopTask encapsulates task stopping sequence.
-func (scheduler *Scheduler) StopTask(task *Task) {
+func (scheduler *Scheduler) StopTask(task *Task) error {
 	if task.stopSignal != nil {
 		close(task.stopSignal)
 		task.stopSignal = nil
 	}
-	scheduler.removeTask(task)
+	return scheduler.removeTask(task)
 }
 
 // removeTask removes Task from the tasks list of the Scheduler.
-func (scheduler *Scheduler) removeTask(scheduledTask *Task) {
+func (scheduler *Scheduler) removeTask(scheduledTask *Task) error {
 	taskIndex := scheduler.FindTaskIndex(scheduledTask)
+	if taskIndex == -1 {
+		return fmt.Errorf("task with id: %s cannot be stopped, because it was not found", scheduledTask.ID)
+	}
 	if len(scheduler.Tasks) <= 1 {
 		scheduler.Tasks = make([]*Task, 0)
 	} else {
 		scheduler.Tasks = append(scheduler.Tasks[:taskIndex], scheduler.Tasks[taskIndex+1:]...)
 	}
+	return nil
 }
 
 // callFunction calls a function dynamically using reflection.

pkg/scheduler/scheduler_test.go

@@ -297,7 +297,7 @@ func TestScheduler_StopTask(t *testing.T) {
 
 	time.Sleep(duration)
 
-	newScheduler.StopTask(newTask)
+	err := newScheduler.StopTask(newTask)
 
 	foundTask := false
 
@@ -307,11 +307,29 @@ func TestScheduler_StopTask(t *testing.T) {
 		}
 	}
 
-	if foundTask {
+	if foundTask && err != nil {
 		t.Fatalf("Task \"%s\" with id \"%s\" has not been stopped.", newTask.Name, newTask.ID)
 	}
 }
 
+// TestScheduler_StopTask_NotExist tests that Scheduler.StopTask method correctly
+// handles situation where provided task doesn't exist.
+func TestScheduler_StopTask_NotExist(t *testing.T) {
+	taskName := "Test Task"
+	intervalSeconds := 5
+	interval := time.Duration(intervalSeconds) * time.Second
+
+	newScheduler := CreateEmptyScheduler()
+	newTask := NewSimpleTask(taskName, interval)
+
+	err := newScheduler.StopTask(newTask)
+	expected := fmt.Sprintf("task with id: %s cannot be stopped, because it was not found", newTask.ID)
+
+	if err.Error() != expected {
+		t.Fatalf("Error has not been thrown for missing task with id %s.", newTask.ID)
+	}
+}
+
 // TestTask_GetFromContext tests that Task.GetFromContext method returns correct
 // value from the Task.context based on the provided key.
 func TestTask_GetFromContext(t *testing.T) {