diff --git a/src/flow/traversible/algorithms/subset.rs b/src/flow/traversible/algorithms/subset.rs
index 0309864..4f530ac 100644
--- a/src/flow/traversible/algorithms/subset.rs
+++ b/src/flow/traversible/algorithms/subset.rs
@@ -84,7 +84,7 @@ impl<'a, T: 'a + MonadFail<'a, ()>, A: 'a + Clone, D: 'a + PartialEq> SubsetCont
         )
     }
 
-    fn test(self) -> T::F<()> {
+    fn test_unoptimised(self) -> T::F<()> {
         let split = self.n_subset.split();
         match self.comparator.compare(&split.2, &self.k_super) {
             Comparison::L => self.on_l(split),
@@ -92,6 +92,44 @@ impl<'a, T: 'a + MonadFail<'a, ()>, A: 'a + Clone, D: 'a + PartialEq> SubsetCont
             Comparison::R => self.on_r(split),
         }
     }
+
+    fn outside_l(&self) -> bool {
+        outside_l(self.comparator, &self.k_l, &self.k_super)
+    }
+
+    fn outside_r(&self) -> bool {
+        outside_r(self.comparator, &self.k_r, &self.k_super)
+    }
+
+    fn test_r_only(self) -> T::F<()> {
+        t_subset_of_t(
+            self.comparator,
+            self.n_subset.to_tree(),
+            self.t_superr,
+            self.k_l,
+            self.k_r,
+        )
+    }
+
+    fn test_l_only(self) -> T::F<()> {
+        t_subset_of_t(
+            self.comparator,
+            self.n_subset.to_tree(),
+            self.t_superl,
+            self.k_l,
+            self.k_r,
+        )
+    }
+
+    fn test_optimised(self) -> T::F<()> {
+        if self.outside_l() {
+            self.test_r_only()
+        } else if self.outside_r() {
+            self.test_l_only()
+        } else {
+            self.test_unoptimised()
+        }
+    }
 }
 
 fn outside_l<A>(comparator: &dyn Comparator<A>, k_l: &Option<A>, k_super: &A) -> bool {
@@ -118,26 +156,20 @@ pub fn n_subset_of_n<'a, T: MonadFail<'a, ()>, A: 'a + Clone, D: 'a + PartialEq>
     k_r: Option<A>,
 ) -> T::F<()> {
     let (t_superl, t_superr, k_super) = n_superset.split();
-    if outside_l(comparator, &k_l, &k_super) {
-        t_subset_of_t(comparator, n_subset.to_tree(), t_superr, k_l, k_r)
-    } else if outside_r(comparator, &k_r, &k_super) {
-        t_subset_of_t(comparator, n_subset.to_tree(), t_superl, k_l, k_r)
-    } else {
-        SubsetContext {
-            comparator,
-            n_subset,
-            n_superset,
-            k_l,
-            k_r,
-            t_superl,
-            t_superr,
-            k_super,
-        }
-        .test()
+    SubsetContext {
+        comparator,
+        n_subset,
+        n_superset,
+        k_l,
+        k_r,
+        t_superl,
+        t_superr,
+        k_super,
     }
+    .test_optimised()
 }
 
-pub fn r_subset_of_r<'a, T: MonadFail<'a, ()>, A: 'a + Clone, D: 'a + PartialEq>(
+pub fn r_subset_of_r_unoptimised<'a, T: MonadFail<'a, ()>, A: 'a + Clone, D: 'a + PartialEq>(
     comparator: &'a dyn Comparator<A>,
     r_subset: Rc<dyn TraversibleBinaryReference<'a, T, A, D>>,
     r_superset: Rc<dyn TraversibleBinaryReference<'a, T, A, D>>,
@@ -151,6 +183,20 @@ pub fn r_subset_of_r<'a, T: MonadFail<'a, ()>, A: 'a + Clone, D: 'a + PartialEq>
     )
 }
 
+fn r_subset_of_r_optimised<'a, T: MonadFail<'a, ()>, A: 'a + Clone, D: 'a + PartialEq>(
+    r_subset: Rc<dyn TraversibleBinaryReference<'a, T, A, D>>,
+    r_superset: Rc<dyn TraversibleBinaryReference<'a, T, A, D>>,
+    comparator: &'a dyn Comparator<A>,
+    k_l: Option<A>,
+    k_r: Option<A>,
+) -> <T as WeakFunctor<'a>>::F<()> {
+    if r_subset.data() == r_superset.data() {
+        T::pure(())
+    } else {
+        r_subset_of_r_unoptimised(comparator, r_subset, r_superset, k_l, k_r)
+    }
+}
+
 pub fn t_subset_of_t<'a, T: MonadFail<'a, ()>, A: 'a + Clone, D: 'a + PartialEq>(
     comparator: &'a dyn Comparator<A>,
     t_subset: Rc<dyn TraversibleBinaryTree<'a, T, A, D>>,
@@ -162,11 +208,7 @@ pub fn t_subset_of_t<'a, T: MonadFail<'a, ()>, A: 'a + Clone, D: 'a + PartialEq>
         (None, _) => T::pure(()),
         (Some(_), None) => T::fail(()),
         (Some(r_subset), Some(r_superset)) => {
-            if r_subset.data() == r_superset.data() {
-                T::pure(())
-            } else {
-                r_subset_of_r(comparator, r_subset, r_superset, k_l, k_r)
-            }
+            r_subset_of_r_optimised(r_subset, r_superset, comparator, k_l, k_r)
         }
     }
 }
diff --git a/src/func/instances/stackless.rs b/src/func/instances/stackless.rs
index 280ab07..7f8a57b 100644
--- a/src/func/instances/stackless.rs
+++ b/src/func/instances/stackless.rs
@@ -302,13 +302,11 @@ mod stackless_test {
         }
     }
 
-    #[ignore]
     #[test]
     fn test_factorial() {
         assert_eq!(factorial(10).evaluate(), 3628800);
     }
 
-    #[ignore]
     #[test]
     fn test_dumb() {
         let n = 1000;
diff --git a/src/mrds/trees/unbalanced.rs b/src/mrds/trees/unbalanced.rs
index ac01d98..cc72250 100644
--- a/src/mrds/trees/unbalanced.rs
+++ b/src/mrds/trees/unbalanced.rs
@@ -205,7 +205,6 @@ mod tests {
         .is_err());
     }
 
-    #[ignore]
     #[test]
     fn test_random_slices() {
         let ctr: Rc<UnbalancedConstructor<instances::result::ResultInstance<()>, _>> =
@@ -255,7 +254,6 @@ mod tests {
         instances::result::ResultInstance<()>,
     >;
 
-    #[ignore]
     #[test]
     fn trace_one_slice() {
         let ctr: Rc<UnbalancedConstructor<TracedMonad, _>> =