Tasty testing of IO return value

Sorry for asking very basic questions concerning tasty (or actually haskell testing in general) but I need some help gettings started.

I have a statement that I need to check the return value of:

> let a = tRunUmeQuery (selectByCount "Word" "Acoustic" "=" ((toInteger 1):[]) Strict)  testdb
> :t a 
a :: IO [[SqlValue]]

So, I would like to make sure that a is a list with a length of exactly 6 (IO 6 then).

> fmap length a
6

What would a testCase that checks this look like?