Able to add a duplicate tag

[randallnhr]

Problem: Users are able to tag a person with an existing tag. Example index 10 cat ng already has a tag cat, but the command tag 10 cat still goes through even though there is no change to the tags.

[nus-se-script]

Team's Response

Sorry but what is the problem with allowing it to go through?

Items for the Tester to Verify

:question: Issue response

Team chose [response.IssueUnclear]

• [x] I disagree

Reason for disagreement: The problem only occurs when a user wants to use the undo function to "remove" a tag that has been assigned.

If a person has an exisiting tag a, allowing the user to reassign a as a tag would cause slight complications as the user might not know that tag a already exist in the person. Therefore when the user calls the undo command thinking he removed the added tag, the exisiting tag a would still be present in the person.

Steps to reproduce:

1. tag 1 a
2. tag 1 a
3. undo (tag a still exist for person at index 1)

---