diff --git a/src/field/extension_field/target.rs b/src/field/extension_field/target.rs
index c00470ac..7efd0f3b 100644
--- a/src/field/extension_field/target.rs
+++ b/src/field/extension_field/target.rs
@@ -19,10 +19,12 @@ impl<const D: usize> ExtensionTarget<D> {
     pub fn frobenius<F: Extendable<D>>(&self, builder: &mut CircuitBuilder<F, D>) -> Self {
         let arr = self.to_target_array();
         let k = (F::ORDER - 1) / (D as u64);
-        let zs = (0..D as u64).map(|i| builder.constant(F::Extension::W.exp(k * i)));
+        let zs = (0..D as u64)
+            .map(|i| builder.constant(F::Extension::W.exp(k * i)))
+            .collect::<Vec<_>>();
 
         let mut res = Vec::with_capacity(D);
-        for (z, a) in zs.zip(arr) {
+        for (z, a) in zs.into_iter().zip(arr) {
             res.push(builder.mul(z, a));
         }
 
diff --git a/src/gadgets/rotate.rs b/src/gadgets/rotate.rs
index acc78734..19230dc0 100644
--- a/src/gadgets/rotate.rs
+++ b/src/gadgets/rotate.rs
@@ -16,8 +16,7 @@ impl<F: Extendable<D>, const D: usize> CircuitBuilder<F, D> {
     }
 
     /// Left-rotates an array `k` times if `b=1` else return the same array.
-    pub fn rotate_fixed(&mut self, b: Target, k: usize, v: Vec<Target>, len: usize) -> Vec<Target> {
-        debug_assert_eq!(v.len(), len);
+    pub fn rotate_fixed(&mut self, b: Target, k: usize, v: &[Target], len: usize) -> Vec<Target> {
         let mut res = Vec::new();
 
         for i in 0..len {
@@ -30,13 +29,56 @@ impl<F: Extendable<D>, const D: usize> CircuitBuilder<F, D> {
     /// Left-rotates an array by `num_rotation`. Assumes that `num_rotation` is range-checked to be
     /// less than `len`.
     /// Note: We assume `len` is less than 8 since we won't use any arity greater than 8 in FRI (maybe?).
-    pub fn rotate(&mut self, num_rotation: Target, mut v: Vec<Target>, len: usize) -> Vec<Target> {
+    pub fn rotate(&mut self, num_rotation: Target, v: &[Target], len: usize) -> Vec<Target> {
+        debug_assert_eq!(v.len(), len);
         let bits = self.split_le_base::<2>(num_rotation, 3);
 
-        v = self.rotate_fixed(bits[0], 1, v, len);
-        v = self.rotate_fixed(bits[1], 2, v, len);
-        v = self.rotate_fixed(bits[2], 4, v, len);
+        let v = self.rotate_fixed(bits[0], 1, v, len);
+        let v = self.rotate_fixed(bits[1], 2, &v, len);
+        let v = self.rotate_fixed(bits[2], 4, &v, len);
 
         v
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::circuit_data::CircuitConfig;
+    use crate::field::crandall_field::CrandallField;
+
+    fn real_rotate(num_rotation: usize, v: &[Target]) -> Vec<Target> {
+        let mut res = v.to_vec();
+        res.rotate_left(num_rotation);
+        res
+    }
+
+    fn test_rotate_given_len(len: usize) {
+        type F = CrandallField;
+        let config = CircuitConfig::large_config();
+        let mut builder = CircuitBuilder::<F, 4>::new(config);
+        let v = (0..len)
+            .map(|_| builder.constant(F::rand()))
+            .collect::<Vec<_>>(); // 416 = 1532 in base 6.
+
+        for i in 0..len {
+            let it = builder.constant(F::from_canonical_usize(i));
+            let rotated = real_rotate(i, &v);
+            let purported_rotated = builder.rotate(it, &v, len);
+
+            for (x, y) in rotated.into_iter().zip(purported_rotated) {
+                builder.assert_equal(x, y);
+            }
+        }
+
+        let data = builder.build();
+        let proof = data.prove(PartialWitness::new());
+    }
+
+    #[test]
+    fn test_rotate() {
+        for i_log in 1..4 {
+            test_rotate_given_len(1 << i_log);
+        }
+    }
+}
diff --git a/src/gadgets/split_base.rs b/src/gadgets/split_base.rs
index 94d3c3bc..f10de655 100644
--- a/src/gadgets/split_base.rs
+++ b/src/gadgets/split_base.rs
@@ -71,10 +71,6 @@ mod tests {
     use super::*;
     use crate::circuit_data::CircuitConfig;
     use crate::field::crandall_field::CrandallField;
-    use crate::fri::FriConfig;
-    use crate::prover::PLONK_BLINDING;
-    use crate::verifier::verify;
-    use anyhow::Result;
 
     #[test]
     fn test_split_base() {