if else statement in derived column in ssis

Hi

I am using a if else statement in derived columnn transformation

like if test_code = 2 then value should be T

and if test_code = 3 then value should be F

AND REST OF THE VALUE SHOULD REMAIN UNCHANGED IN THE TEST_CODE COLUMN

I am using following expression

test_code = 2 ? "T":"F"

THIS CODE WILL CHANGE ALL THE VALUE TO "F" IF IT is not 2.

How can we bulild such an expression

Please Help Thanks