1 files changed, 31 insertions, 0 deletions
diff --git a/stdlib/source/spec/lux/abstract/monoid.lux b/stdlib/source/spec/lux/abstract/monoid.lux
new file mode 100644
index 000000000..eca057360
--- /dev/null
+++ b/stdlib/source/spec/lux/abstract/monoid.lux
@@ -0,0 +1,31 @@
+(.module:
+  [lux #*
+   ["_" test (#+ Test)]
+   [abstract
+    [monad (#+ do)]]
+   [math
+    ["." random (#+ Random)]]]
+  {1
+   ["." /
+    [//
+     [equivalence (#+ Equivalence)]]]})
+
+(def: #export (spec (^open "/@.") (^open "/@.") gen-sample)
+  (All [a] (-> (Equivalence a) (/.Monoid a) (Random a) Test))
+  (do random.monad
+    [sample gen-sample
+     left gen-sample
+     mid gen-sample
+     right gen-sample]
+    (<| (_.with-cover [/.Monoid])
+        ($_ _.and
+            (_.test "Left identity."
+                    (/@= sample
+                         (/@compose /@identity sample)))
+            (_.test "Right identity."
+                    (/@= sample
+                         (/@compose sample /@identity)))
+            (_.test "Associativity."
+                    (/@= (/@compose left (/@compose mid right))
+                         (/@compose (/@compose left mid) right)))
+            ))))