diff --git a/src/func/instances/effect.rs b/src/func/instances/effect.rs
index 72a7dc5..9610f90 100644
--- a/src/func/instances/effect.rs
+++ b/src/func/instances/effect.rs
@@ -22,7 +22,7 @@ pub trait Effect: Send {
 }
 
 /// Value and related metadata.
-#[derive(Clone)]
+#[derive(Debug, Clone, PartialEq, Eq)]
 pub struct WithEffect<A, E> {
     pub value: A,
     pub effect: E,