1 files changed, 31 insertions, 0 deletions
diff --git a/stdlib/source/spec/lux/abstract/functor/contravariant.lux b/stdlib/source/spec/lux/abstract/functor/contravariant.lux
new file mode 100644
index 000000000..b21e28e68
--- /dev/null
+++ b/stdlib/source/spec/lux/abstract/functor/contravariant.lux
@@ -0,0 +1,31 @@
+(.module:
+  [lux #*
+   [abstract
+    [equivalence (#+ Equivalence)]
+    [monad (#+ do)]]
+   [data
+    [number
+     ["n" nat]]]
+   [control
+    ["." function]]
+   [math
+    ["." random]]
+   ["_" test (#+ Test)]]
+  {1
+   ["." / (#+ Functor)]})
+
+(def: (identity equivalence value (^open "/@."))
+  (All [f a] (-> (Equivalence (f a)) (f a) (Functor f) Test))
+  (_.test "Law of identity."
+          (equivalence
+           (/@map function.identity value)
+           value)))
+
+(def: #export (spec equivalence value functor)
+  (All [f a] (-> (Equivalence (f a)) (f a) (Functor f) Test))
+  (do random.monad
+    [sample random.nat]
+    (<| (_.with-cover [/.Functor])
+        ($_ _.and
+            (..identity equivalence value functor)
+            ))))