Who am I?

I'm an object...
I'm used by people who wear white...
I'm a tool for a professional...
I perform lots of test for a person...
When children see me, they will think i'm a toy...

Who am i?

PS: If you have the right answer, you will get a free test... :)

What is this tool use for?

Hint: 

It used in the kitchen. 

It related to the picture below.

My US colleague gave me on my last trip to US.

So, what do you think? Do you know the name of the tool and its purpose? Dropped me a comment... :-> Will review the answer later ...