Added test for base field properties to improve coverage.
Added test for base field properties to improve coverage.

Xender/wtforms,pawl/wtforms,cklein/wtforms,pawl/wtforms,Aaron1992/wtforms,Aaron1992/wtforms,subyraman/wtforms,jmagnusson/wtforms,wtforms/wtforms,crast/wtforms,hsum/wtforms,skytreader/wtforms