An email address is composed of two parts: a username and a domain name (e.g. "gmail.com"). A full email address
has the form "
Write a function buildEmailAddress that takes two String parameters representing a username and a domain name
and returns a String representing the email address formed from these parts.
For example, if the username parameter is "abc" and the domain name parameter is "gmail.com", you should return
"[email protected]".
You're challenge is to write tests for this problem described above.