move test helpers to ‘Util’ module

So we can reuse them to test other modules.

tests/Prim.hs

@@ -332,16 +332,3 @@ prop_user_state n m = runParser p 0 "" "" === Right (n + m)
 prop_user_backtrack :: Integer -> Integer -> Property
 prop_user_backtrack n m = runParser p 0 "" "" === Right n
   where p = setState n >> lookAhead (setState m >> eof) >> getState
-
--- Helpers
-
-infix 4 /=\
-
-(/=\) :: (Eq a, Show a) => Parser a -> a -> Property
-p /=\ x = simpleParse p "" === Right x
-
-abcRow :: Int -> Int -> Int -> String
-abcRow a b c = replicate a 'a' ++ replicate b 'b' ++ replicate c 'c'
-
-abcRow' :: Bool -> Bool -> Bool -> String
-abcRow' a b c = abcRow (fromEnum a) (fromEnum b) (fromEnum c)

tests/Util.hs

@@ -32,6 +32,9 @@ module Util
   , simpleParse
   , checkChar
   , checkString
+  , (/=\)
+  , abcRow
+  , abcRow'
   , posErr
   , uneCh
   , uneStr
@@ -102,6 +105,29 @@ checkString p a' l s' = checkParser p (w a' 0 s') s'
           | otherwise = posErr 0 s' [uneStr (take i' s'), exSpec l]
             where i'  = succ i
 
+infix 4 /=\
+
+-- | @p /=\\ x@ runs parser @p@ on empty input and compares its result
+-- (which should be successful) with @x@. Succeeds when the result is equal
+-- to @x@, prints counterexample on failure.
+
+(/=\) :: (Eq a, Show a) => Parser a -> a -> Property
+p /=\ x = simpleParse p "" === Right x
+
+-- | @abcRow a b c@ generates string consisting of character “a” repeated
+-- @a@ times, character “b” repeated @b@ times, and finally character “c”
+-- repeated @c@ times.
+
+abcRow :: Int -> Int -> Int -> String
+abcRow a b c = replicate a 'a' ++ replicate b 'b' ++ replicate c 'c'
+
+-- | @abcRow' a b c@ generates string that includes character “a” if @a@ is
+-- 'True', then optionally character “b” if @b@ is 'True', then character
+-- “c” if @c@ is 'True'.
+
+abcRow' :: Bool -> Bool -> Bool -> String
+abcRow' a b c = abcRow (fromEnum a) (fromEnum b) (fromEnum c)
+
 -- | @posErr pos s ms@ is an easy way to model result of parser that
 -- fails. @pos@ is how many tokens (characters) has been consumed before
 -- failure. @s@ is input of the parser. @ms@ is a list, collection of