CREATE DATABASE TestDB
GO
SELECT Name from sys.Databases
GO
Name
----------
master
tempdb
model
msdb
USE TestDB
GO
EXEC msdb.dbo.sp_delete_database_backuphistory @database_name = N'yourdbname'
GO
USE [master]
GO
ALTER DATABASE [yourdbname] SET SINGLE_USER WITH ROLLBACK IMMEDIATE
GO
DROP DATABASE [yourdbname]
GO