Write failing unit test to cover task hierarchy bug
Start writing logic for finding last child, given a random parent
Remove commented-out code
Remove unused method
Get final child when there is more than one child
Move position of task.save in test
Refactor next step test
Refactor test of tasks with multiple children
Fetch task at bottom of hierarchy when looking for the next step
Ignore completed tasks when searching task hierarchy
Remove test which was incorrect because it did not take into account completed children
Call new method for finding the next step of a task from the controller