Insert/Update SQL Server Stored Procedure
As a very generic answer, if you want to test code of this nature without actually changing the data then it is possible to run your code, query the results, and then undo any changes before they are committed.

-- Begin a new transaction
begin transaction

    -- Show initial data
    select * from [dbo].[employee]


    -- Your statement to change the data
    MERGE [dbo].[employee] AS [Target]
    ....
    ....
    ....


    -- Show the new data
    select * from [dbo].[employee]


-- Rollback the transaction, leaving the data in its original state.
rollback transaction