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-rw-r--r--test/Xanthous/DataSpec.hs9
1 files changed, 8 insertions, 1 deletions
diff --git a/test/Xanthous/DataSpec.hs b/test/Xanthous/DataSpec.hs
index 6b94e6a0582a..26a862baa6a6 100644
--- a/test/Xanthous/DataSpec.hs
+++ b/test/Xanthous/DataSpec.hs
@@ -26,7 +26,14 @@ test = testGroup "Xanthous.Data"
         directionOf pos (move dir pos) == dir
     , testProperty "diffPositions is add inverse" $ \pos₁ pos₂ ->
         diffPositions pos₁ pos₂ == addPositions pos₁ (invert pos₂)
-
+    , testGroup "isUnit"
+      [ testProperty "double direction is never unit" $ \dir ->
+          not . isUnit $ move dir (asPosition dir)
+      , testCase "examples" $ do
+          isUnit (Position 1 1) @? "not . isUnit $ Position 1 1"
+          isUnit (Position 0 (-1)) @? "not . isUnit $ Position 0 (-1)"
+          (not . isUnit) (Position 1 13) @? "isUnit $ Position 1 13"
+      ]
     ]
   , testGroup "Direction"
     [ testProperty "opposite is involutive" $ \(dir :: Direction) ->