E736. Undo Functionality for Expertiza

Team Members

Undo allows the user to undo their most recent actions for any items that offer the undo functionality.
The undo of file submissions was not required; however, we did or did not do these....depends on if we complete it...
If an undo is attempted on an item already modified by another user, a message is displayed stating why undo cannot be performed. Otherwise, the user is able to undo any changes to an item with the undo functionality.
When multiple actions are performed in one step, the undo functionality groups all of the changes together for the purposes of restoring all items affected by the action previously performed.

DRY
- "Don't Repeat Yourself" practice will be followed.
Memento
- The memento pattern is a software design pattern that provides the ability to restore an object to its previous state (undo via rollback). The memento pattern is implemented with two objects: the originator and a caretaker. The originator is some object that has an internal state. The caretaker is going to do something to the originator, but wants to be able to undo the change. The caretaker first asks the originator for a memento object. Then it does whatever operation (or sequence of operations) it was going to do. To roll back to the state before the operations, it returns the memento object to the originator. The memento object itself is an opaque object (one which the caretaker cannot, or should not, change). When using this pattern, care should be taken if the originator may change other objects or resources - the memento pattern operates on a single object. Classic examples of the memento pattern include the seed of a pseudorandom number generator (it will always produce the same sequence thereafter when initialized with the seed state) and the state in a finite state machine.
- The Memento pattern will be followed through open-source Ruby gems leveraged by the project.

Every class method modified will be tested via unit test.
Every new method added will be tested via at least one unit test.
All test methods shall be named with an appropriately descriptive name that is not too long.

The following functional test plans will be followed for all items enhanced with the Undo functionality:
- Test that an item may be changed, then undo performed successfully.
- Test that a sequence of changes may be performed by one user, then undo performed successfully for each action from the sequence.
- Test that an item may be changed by one user, changed again by another user, then undo performed by the original user will display a failure message with description.