Reading the input can be do easily as below. By the way, despite of the fact that problem states that "You are given a set of unique ordered pairs constituting a relation", the test cases actually contain not-ordered pairs...

main :: IO ()
main = do  
  t <- readLn
  replicateM_ t $ do 
    n <- readLn
    l <- replicateM n $ do 
      xy <- getLine
      let [x,y] = words xy
      return (read x, read y)
    if solve l then putStrLn "YES" else putStrLn "NO"

where solve is the function that returns True is it is a valid relation and False otherwise