diff --git a/src/func/instances/composition.rs b/src/func/instances/composition.rs
index 81d960e..2229fe2 100644
--- a/src/func/instances/composition.rs
+++ b/src/func/instances/composition.rs
@@ -210,6 +210,15 @@ mod composition_tests {
         }
     }
 
+    impl<'a> test_suite::FailTestSuite<'a, i32> for T {
+        fn sample_fail<F: FnMut(Arc<dyn 'a + Send + Sync + Fn() -> i32>)>(mut f: F) {
+            f(Arc::new(|| 0));
+            f(Arc::new(|| 1));
+            f(Arc::new(|| 2));
+            f(Arc::new(|| 3));
+        }
+    }
+
     #[test]
     fn monad_follows_laws() {
         test_suite::monad_follows_laws::<T>().unwrap();
@@ -220,6 +229,11 @@ mod composition_tests {
         test_suite::shared_follows_laws::<T>().unwrap();
     }
 
+    #[test]
+    fn fail_follows_laws() {
+        test_suite::fail_functor_follows_laws::<T, _>().unwrap();
+    }
+
     #[test]
     fn select_second() {
         type T = CompositionInstance<TryFutureInstance<i32>, ResultInstance<i32>>;
diff --git a/src/func/instances/result.rs b/src/func/instances/result.rs
index f2515bb..acb0428 100644
--- a/src/func/instances/result.rs
+++ b/src/func/instances/result.rs
@@ -276,6 +276,15 @@ mod result_tests {
         }
     }
 
+    impl<'a> test_suite::FailTestSuite<'a, i32> for T {
+        fn sample_fail<F: FnMut(Arc<dyn 'a + Send + Sync + Fn() -> i32>)>(mut f: F) {
+            f(Arc::new(|| 0));
+            f(Arc::new(|| 1));
+            f(Arc::new(|| 2));
+            f(Arc::new(|| 3));
+        }
+    }
+
     #[test]
     fn monad_follows_laws() {
         test_suite::monad_follows_laws::<T>().unwrap();
@@ -285,4 +294,9 @@ mod result_tests {
     fn shared_follows_laws() {
         test_suite::shared_follows_laws::<T>().unwrap();
     }
+
+    #[test]
+    fn fail_follows_laws() {
+        test_suite::fail_functor_follows_laws::<T, _>().unwrap();
+    }
 }
diff --git a/src/func/instances/tryfuture.rs b/src/func/instances/tryfuture.rs
index 77f2e6c..f26f32f 100644
--- a/src/func/instances/tryfuture.rs
+++ b/src/func/instances/tryfuture.rs
@@ -239,6 +239,15 @@ mod tryfuture_tests {
         }
     }
 
+    impl<'a> test_suite::FailTestSuite<'a, i32> for T {
+        fn sample_fail<F: FnMut(Arc<dyn 'a + Send + Sync + Fn() -> i32>)>(mut f: F) {
+            f(Arc::new(|| 0));
+            f(Arc::new(|| 1));
+            f(Arc::new(|| 2));
+            f(Arc::new(|| 3));
+        }
+    }
+
     #[test]
     fn monad_follows_laws() {
         test_suite::monad_follows_laws::<T>().unwrap();
@@ -258,4 +267,9 @@ mod tryfuture_tests {
     fn shared_follows_laws() {
         test_suite::shared_follows_laws::<T>().unwrap();
     }
+
+    #[test]
+    fn fail_follows_laws() {
+        test_suite::fail_functor_follows_laws::<T, _>().unwrap();
+    }
 }