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-rw-r--r--test/Xanthous/Data/EntityMapSpec.hs5
1 files changed, 4 insertions, 1 deletions
diff --git a/test/Xanthous/Data/EntityMapSpec.hs b/test/Xanthous/Data/EntityMapSpec.hs
index 00bf1500466a..2e9714a44eb7 100644
--- a/test/Xanthous/Data/EntityMapSpec.hs
+++ b/test/Xanthous/Data/EntityMapSpec.hs
@@ -15,7 +15,10 @@ test = localOption (QuickCheckTests 20)
   $ testGroup "Xanthous.Data.EntityMap"
   [ testBatch $ monoid @(EntityMap Int) mempty
   , testGroup "Deduplicate"
-    [ testBatch $ monoid @(Deduplicate Int) mempty
+    [ testGroup "Semigroup laws"
+      [ testProperty "associative" $ \(a :: Deduplicate (EntityMap Int)) b c ->
+          a <> (b <> c) === (a <> b) <> c
+      ]
     ]
   , testGroup "Eq laws"
     [ testProperty "reflexivity" $ \(em :: EntityMap Int) ->