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diff --git a/users/glittershark/xanthous/test/Xanthous/Data/EntityMap/GraphicsSpec.hs b/users/glittershark/xanthous/test/Xanthous/Data/EntityMap/GraphicsSpec.hs
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+++ b/users/glittershark/xanthous/test/Xanthous/Data/EntityMap/GraphicsSpec.hs
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+--------------------------------------------------------------------------------
+module Xanthous.Data.EntityMap.GraphicsSpec (main, test) where
+--------------------------------------------------------------------------------
+import Test.Prelude
+import Data.Aeson
+--------------------------------------------------------------------------------
+import Xanthous.Game.State
+import Xanthous.Data
+import Xanthous.Data.EntityMap
+import Xanthous.Data.EntityMap.Graphics
+import Xanthous.Entities.Environment (Wall(..))
+--------------------------------------------------------------------------------
+
+main :: IO ()
+main = defaultMain test
+
+test :: TestTree
+test = testGroup "Xanthous.Data.EntityMap.Graphics"
+  [ testGroup "visiblePositions"
+    [ testProperty "one step in each cardinal direction is always visible"
+      $ \pos (Cardinal dir) (Positive r) (wallPositions :: Set Position)->
+          pos `notMember` wallPositions ==>
+          let em = review _EntityMap . map (, Wall) . toList $ wallPositions
+              em' = em & atPosition (move dir pos) %~ (Wall <|)
+              poss = visiblePositions pos r em'
+          in counterexample ("visiblePositions: " <> show poss)
+             $ move dir pos `member` poss
+    , testGroup "bugs"
+      [ testCase "non-contiguous bug 1"
+        $ let charPos = Position 20 20
+              gormlakPos = Position 17 19
+              em = insertAt gormlakPos TestEntity
+                   . insertAt charPos TestEntity
+                   $ mempty
+              visPositions = visiblePositions charPos 12 em
+          in (gormlakPos `member` visPositions) @?
+             ( "not ("
+             <> show gormlakPos <> " `member` "
+             <> show visPositions
+             <> ")"
+             )
+      ]
+    ]
+  ]
+
+--------------------------------------------------------------------------------
+
+data TestEntity = TestEntity
+  deriving stock (Show, Eq, Ord, Generic)
+  deriving anyclass (ToJSON, FromJSON, NFData)
+
+instance Brain TestEntity where
+  step _ = pure
+instance Draw TestEntity
+instance Entity TestEntity where
+  description _ = ""
+  entityChar _ = "e"