diff --git a/src/rstd.rs b/src/rstd.rs
index 46aef72..ae84ec0 100644
--- a/src/rstd.rs
+++ b/src/rstd.rs
@@ -39,6 +39,15 @@ pub(crate) fn hex(point: &Hash) -> impl '_ + Display {
     Hex { point }
 }
 
+#[cfg(test)]
+#[test]
+fn hex_test() {
+    assert_eq!(
+        hex(&(0..32).collect::<Vec<_>>().try_into().unwrap()).to_string(),
+        "000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f",
+    );
+}
+
 impl Display for Address {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         write!(f, "{}@{}", hex(&self.point), self.index)