Would you mind being a little more specific?
What is the "business logic" to get to the result you're looking for?
It's unknown, whether the value is "2.Test." or "Test.".
It is also unknown, whether you're looking for identical characters at position 3 to 7 (or 1 to 4, respectively), or for the substring "Test", regardless of the position within the string itself.
Please help us help you.