Added a test: see if my parsers aren't modifying the input.

test/Main.purs

@@ -1,6 +1,6 @@
 module Test.Main where
 
-import Prelude (Unit, discard, show, ($), (<>))
+import Prelude (Unit, discard, show, ($), (<>), (==))
 import Data.Either (Either(..))
 import Data.Maybe (Maybe(..), maybe)
 import Data.String.CodeUnits (fromCharArray)
@@ -17,6 +17,29 @@ import GenericParser.IPAddress as IP
 import GenericParser.EmailAddress as E
 import Test.TestValues as T
 
+run :: forall e v. Parser e v -> String -> P.Result e v
+run (Parser p) str = p { string: str, position: 0 }
+
+data COMPARISON = SAME | DIFFERENT | FAILED
+compare_results :: forall e v. Parser e v -> Parser e v -> String -> COMPARISON
+compare_results p1 p2 str
+  = let e1 = run p1 str
+        e2 = run p2 str
+    in case e1, e2 of
+         Right r1, Right r2 -> if r1.suffix == r2.suffix
+                               then SAME
+                               else DIFFERENT
+         _, _ -> FAILED
+
+compare_parsers :: forall e v. String -> Parser e v -> Parser e v -> String -> Effect Unit
+compare_parsers s p1 p2 str
+  = log $ s <> " "
+          <> case compare_results p1 p2 str of
+               SAME -> "SAME"
+               DIFFERENT -> "DIFFERENT"
+               FAILED -> "FAILED"
+          <> " [" <> str <>"] "
+
 logtest :: forall e v. String -> Parser e v -> String -> (v -> String) -> (e -> String) -> Effect Unit
 logtest fname (Parser p) str r e = do
   log $ "(" <> fname <> ") parsing '" <> str <> "': "
@@ -99,3 +122,6 @@ main = do
   let quotedstrings = [ """" "spaces?""", """ " " """ ]
   test_series "E.quoted_string---------------" E.quoted_string id showerror_email quotedstrings
   test_series "P.read_input (E.quoted_string)" (P.read_input E.quoted_string) id showerror_email quotedstrings
+
+  log "Does parsers behave correctly (give the exact same input)?"
+  foreachE T.valid_email_addresses_short (\s -> compare_parsers "E.address" (P.read_input E.address) E.address s)