DUPLICATE_VALUE, duplicate value found:
duplicates value on record with id:
:  when inserting Topic in a Test method
|Knowledge Article Number||000220923|
|Description||When inserting a Topic in a test method, if the name of the topic matches any existing topics in that community you'll see the following error:
DUPLICATE_VALUE, duplicate value found: <unknown> duplicates value on record with id: <unknown>:
Please note: "SeeAllData" will not have any affect on topics in communities.
|Resolution||Topics cannot be duplicate, even in test data, just like usernames.
Change the name of the Topic that you are trying to insert in the test method. Make sure there are no duplicate topics in any given community.