- Tested monad transformer for Error.

1 files changed, 13 insertions, 1 deletions

diff --git a/stdlib/test/test/lux/data/error.lux b/stdlib/test/test/lux/data/error.lux
index 7cc7c2f4c..6127c37c1 100644
--- a/stdlib/test/test/lux/data/error.lux
+++ b/stdlib/test/test/lux/data/error.lux
@@ -7,7 +7,8 @@
   lux
   (lux (codata [io])
        (control monad)
-       (data ["&" error])
+       (data text/format
+             ["&" error])
        pipe)
   lux/test)
 
@@ -47,3 +48,14 @@
                          (case> (#;Left "YOLO") true _ false))
                      ))
         )))
+
+(test: "Monad transformer"
+  (let [lift (&;lift-error io;Monad<IO>)
+        (^open "io/") io;Monad<IO>]
+    (assert "Can add error functionality to any monad."
+            (|> (io;run (do (&;ErrorT io;Monad<IO>)
+                          [a (lift (io/wrap 123))
+                           b (wrap 456)]
+                          (wrap (i.+ a b))))
+                (case> (#;Right 579) true
+                       _ false)))))