shorten tests using Either operations

tests/UnitTest.hs

@@ -10,6 +10,7 @@ import qualified System.Exit as Exit
 import Control.Exception
 import Debug.Trace (trace, traceShow)
 import qualified Data.Time
+import Data.Either
 
 preamble = [r|
 <?xml version="1.0" encoding="UTF-8"?>
@@ -55,25 +56,26 @@ onepointWithAttrs = wrap [r|
 |]
 
 test1 = TestCase $
-        case Track.parse (wrap "") of
-          Left err -> assertFailure (displayException err)
-          Right t -> assertEqual "empty track has no elements"
-                     0 (Track.length t)
+        either
+        (assertFailure . displayException)
+        (\ t -> assertEqual "empty track has no elements"
+                0 (Track.length t))
+        (Track.parse (wrap ""))
 
 testMalformed = TestCase $
-        case Track.parse (wrap "<dgdsfg>>") of
-          Left err -> assertBool "syntax error" True
-          Right _ -> assertFailure "no error message parsing bad xml"
+                let trk = Track.parse (wrap "<dgdsfg>>")
+                in assertBool "catches syntax error" (isLeft trk)
 
 test2 = TestCase $
-        case Track.parse onepoint
-        of
-          Left err -> assertFailure (displayException err)
-          Right (p:ps) ->
+        either
+        (assertFailure . displayException)
+        (\ trk -> case trk of
+          p:_ ->
             assertEqual "matches lat/lon"
              (Track.Pos 51.0 (-0.1))
              (Track.pos p)
-          Right [] -> assertFailure "no points"
+          [] -> assertFailure "no points")
+        (Track.parse onepoint)
 
 test3 = TestCase $
         case Track.parse onepoint