Extracting bytes function into its own utility

src/utils/bytes.rs

@@ -0,0 +1,64 @@
+pub fn zero_pad_to_32(mut bytes: Vec<u8>) -> [u8; 32] {
+    assert!(bytes.len() <= 32);
+    if bytes.len() != 32 {
+        bytes.resize(32, 0);
+    }
+    let mut padded_bytes = [0; 32];
+    padded_bytes.copy_from_slice(&bytes[..]);
+    assert!(padded_bytes.len() == 32);
+    padded_bytes
+}
+
+#[cfg(test)]
+mod zero_padding_to_32_bytes {
+    use super::*;
+
+    #[cfg(test)]
+    mod with_empty_input {
+        use super::*;
+
+        #[test]
+        fn it_returns_32_zeros() {
+            let input = vec![];
+            let result = zero_pad_to_32(input);
+            assert_eq!([0u8; 32], result);
+        }
+    }
+
+    #[cfg(test)]
+    mod with_all_bytes_set_to_1 {
+        use super::*;
+        #[test]
+        fn it_returns_32_ones() {
+            let input = vec![1u8; 32];
+            let result = zero_pad_to_32(input);
+            assert_eq!([1u8; 32], result);
+        }
+    }
+
+    #[cfg(test)]
+    mod with_3_bytes_set {
+        use super::*;
+        #[test]
+        fn it_returns_input_zero_padded_to_32_bytes() {
+            let input = vec![1u8; 3];
+            let result = zero_pad_to_32(input);
+            let expected_content = vec![
+                1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+                0, 0, 0, 0,
+            ];
+            assert_eq!(expected_content, result.to_vec());
+        }
+    }
+
+    #[cfg(test)]
+    mod with_oversized_input {
+        use super::*;
+        #[test]
+        #[should_panic]
+        fn it_panics() {
+            let input = vec![1u8; 33];
+            zero_pad_to_32(input);
+        }
+    }
+}

src/utils/mod.rs

@@ -0,0 +1 @@
+pub mod bytes;