Some times ago, when I used Skype for the first time, I mistakenly removed Skype Test Call from my contact. I don't see the reason to keep it on my contact list until one day I face a problem. My microphone is broken and I just buy the new one. However , when I need to test if it's working with Skype, I started to look it on my contact list. It's not good to call one of my friends just to say that I want to test my microphone with Skype. Therefore, I try to add it back by searching it.
Searching it with terms [Skype Test Call] and I got many results duplicated. Which one is the original ? I can't decide it. Think again about it, I try to create another Skype account. Of course, it's just for getting Skype id for that Skype Test Call. After I created it, I see it on the contact list and its Skype ID is : echo123.
That's it, I logged out from this new account. Then I login with my usual Skype ID and search [echo123] through the menu. It returns many search result too. However, since Skype ID is unique, I just added echo123 to my contact. It approved me and I used it to test my new microphone with Skype.
Conclusion : A little thing can be the big one in certain situation. So, think before doing it. But don't worry if you made a mistake. At least, it will give you new experience. And experience is the best teacher, isn't it ?