Looks a lot like a turnip...

...a turnip...??

I definitely wasn't expecting a turnip..

Um.. do turnips flower? How will I be able to know if it is indeed a turnip without pulling it up??

All plants flower. Wait until it flowers, the flower is usually a dead giveaway to ID.

It's possible it just looks a lot like it. I'm growing them in my garden and they look just like that.

Once it gets too hot a turnip will bolt. It's a brassica, flowers I believe are yellow or white.

Here is a link that might be useful: Turnip images

It could be Sinapis arvensis, Sinapis alba or some similar wild mustard. Also Brassicas. The flowers will tell.