diff --git a/t/form-extension.t b/t/form-extension.t
new file mode 100644
index 00000000..18cb0c12
--- /dev/null
+++ b/t/form-extension.t
@@ -0,0 +1,15 @@
+#!perl -T
+use 5.006;
+use strict;
+use warnings;
+use Language::Bel::Test::DSL;
+
+__DATA__
+
+> (form hello ((e) a s r m)
+    (mev s (cons (append "Hello " e "!") r) m))
+!IGNORE: output of form definition
+
+> (bel '(hello "world"))
+"Hello world!"
+