Precondition:
The user has opened the app and selected a map.
Main success scenario:
The user sees events represented on the scrollbar of the timeline feature, allowing them to understand how the map changed over time.
Events include:
addition of an element to the map (colored green)
removal of an element from the map (colored red)
the events are represented by a visual indication directly at the day/month/year on the sliders.
the timeline can be scaled vertically for touch screen usage.
if there is no event at a certain point in time, the graph is empty. That means that 0 events should lead to no visual indication, so that 0 and 1 can be easily distinguished.
Alternative scenario:
The user has not yet added/removed any elements, therefore no events are visible on the timeline.
Error scenario:
There is an error in the timeline display or event loading functionality.
In this case, the app displays an error message and allows the user to try again.
Postcondition:
The user successfully sees the events on the timeline scrollbar.