diff --git a/halo2_gadgets/Cargo.toml b/halo2_gadgets/Cargo.toml
index ebf8dec62..565f02dba 100644
--- a/halo2_gadgets/Cargo.toml
+++ b/halo2_gadgets/Cargo.toml
@@ -40,6 +40,7 @@ plotters = { version = "0.3.0", default-features = false, optional = true }
 
 [dev-dependencies]
 criterion = "0.3"
+halo2_poseidon = { version = "0.0", path = "../halo2_poseidon", default-features = false, features = ["test-dependencies"] }
 proptest = "1.0.0"
 
 [target.'cfg(unix)'.dev-dependencies]
diff --git a/halo2_gadgets/src/poseidon.rs b/halo2_gadgets/src/poseidon.rs
index 07ba0df0a..6538f330c 100644
--- a/halo2_gadgets/src/poseidon.rs
+++ b/halo2_gadgets/src/poseidon.rs
@@ -148,13 +148,7 @@ impl<
     pub fn new(chip: PoseidonChip, mut layouter: impl Layouter<F>) -> Result<Self, Error> {
         chip.initial_state(&mut layouter).map(|state| Sponge {
             chip,
-            mode: Absorbing(
-                (0..RATE)
-                    .map(|_| None)
-                    .collect::<Vec<_>>()
-                    .try_into()
-                    .unwrap(),
-            ),
+            mode: Absorbing::init_empty(),
             state,
             _marker: PhantomData::default(),
         })
diff --git a/halo2_gadgets/src/poseidon/pow5.rs b/halo2_gadgets/src/poseidon/pow5.rs
index 704bda1da..61ccd2415 100644
--- a/halo2_gadgets/src/poseidon/pow5.rs
+++ b/halo2_gadgets/src/poseidon/pow5.rs
@@ -341,7 +341,7 @@ impl<
 
                 // Load the input into this region.
                 let load_input_word = |i: usize| {
-                    let (cell, value) = match input.0[i].clone() {
+                    let (cell, value) = match input.get(i).expect("i in range").clone() {
                         Some(PaddedWord::Message(word)) => (word.cell(), word.value().copied()),
                         Some(PaddedWord::Padding(padding_value)) => {
                             let cell = region
@@ -394,14 +394,7 @@ impl<
     }
 
     fn get_output(state: &State<Self::Word, WIDTH>) -> Squeezing<Self::Word, RATE> {
-        Squeezing(
-            state[..RATE]
-                .iter()
-                .map(|word| Some(word.clone()))
-                .collect::<Vec<_>>()
-                .try_into()
-                .unwrap(),
-        )
+        Squeezing::init_with(state[..RATE].try_into().unwrap())
     }
 }
 
diff --git a/halo2_poseidon/Cargo.toml b/halo2_poseidon/Cargo.toml
index 25b7784ea..2831342e1 100644
--- a/halo2_poseidon/Cargo.toml
+++ b/halo2_poseidon/Cargo.toml
@@ -19,3 +19,6 @@ bitvec = "1"
 ff = "0.13"
 group = "0.13"
 pasta_curves = "0.5"
+
+[features]
+test-dependencies = []
diff --git a/halo2_poseidon/src/lib.rs b/halo2_poseidon/src/lib.rs
index 6c8d133dc..be887170d 100644
--- a/halo2_poseidon/src/lib.rs
+++ b/halo2_poseidon/src/lib.rs
@@ -12,8 +12,8 @@ pub(crate) mod fq;
 pub(crate) mod grain;
 pub(crate) mod mds;
 
-#[cfg(test)]
-pub(crate) mod test_vectors;
+#[cfg(any(test, feature = "test-dependencies"))]
+pub mod test_vectors;
 
 mod p128pow5t3;
 pub use p128pow5t3::P128Pow5T3;
@@ -21,7 +21,7 @@ pub use p128pow5t3::P128Pow5T3;
 use grain::SboxType;
 
 /// The type used to hold permutation state.
-pub(crate) type State<F, const T: usize> = [F; T];
+pub type State<F, const T: usize> = [F; T];
 
 /// The type used to hold sponge rate.
 pub(crate) type SpongeRate<F, const RATE: usize> = [Option<F>; RATE];
@@ -175,7 +175,17 @@ impl<F, const RATE: usize> SpongeMode for Absorbing<F, RATE> {}
 impl<F, const RATE: usize> SpongeMode for Squeezing<F, RATE> {}
 
 impl<F: fmt::Debug, const RATE: usize> Absorbing<F, RATE> {
-    pub(crate) fn init_with(val: F) -> Self {
+    pub fn init_empty() -> Self {
+        Self(
+            (0..RATE)
+                .map(|_| None)
+                .collect::<Vec<_>>()
+                .try_into()
+                .unwrap(),
+        )
+    }
+
+    pub fn init_with(val: F) -> Self {
         Self(
             iter::once(Some(val))
                 .chain((1..RATE).map(|_| None))
@@ -184,6 +194,22 @@ impl<F: fmt::Debug, const RATE: usize> Absorbing<F, RATE> {
                 .unwrap(),
         )
     }
+
+    pub fn get(&self, n: usize) -> Option<Option<&F>> {
+        self.0.iter().nth(n).map(|x| x.as_ref())
+    }
+}
+
+impl<F: fmt::Debug, const RATE: usize> Squeezing<F, RATE> {
+    pub fn init_with(vals: [F; RATE]) -> Self {
+        Self(
+            vals.into_iter()
+                .map(Some)
+                .collect::<Vec<_>>()
+                .try_into()
+                .unwrap(),
+        )
+    }
 }
 
 /// A Poseidon sponge.