lib: Add test for composeExtensions

1 files changed, 10 insertions, 0 deletions

diff --git a/lib/tests.nix b/lib/tests.nix
index 1a9a5accd1c03..d93cadf253351 100644
--- a/lib/tests.nix
+++ b/lib/tests.nix
@@ -277,4 +277,14 @@ runTests {
     expected = [ "2001" "db8" "0" "0042" "" "8a2e" "370" "" ];
   };
 
+  testComposeExtensions = {
+    expr = let obj = makeExtensible (self: { foo = self.bar; });
+               f = self: super: { bar = false; baz = true; };
+               g = self: super: { bar = super.baz or false; };
+               f_o_g = composeExtensions f g;
+               composed = obj.extend f_o_g;
+           in composed.foo;
+    expected = true;
+  };
+
 }