diff --git a/crates/primitives/src/consts.rs b/crates/primitives/src/consts.rs
index 396905274b..008068f3a0 100644
--- a/crates/primitives/src/consts.rs
+++ b/crates/primitives/src/consts.rs
@@ -6,37 +6,35 @@ pub const WORD_SIZE: usize = 4;
 
 /// Converts a slice of words to a byte vector in little endian.
 pub fn words_to_bytes_le_vec(words: &[u32]) -> Vec<u8> {
-    words.iter().flat_map(|word| word.to_le_bytes().to_vec()).collect::<Vec<_>>()
+    words.iter().flat_map(|&word| word.to_le_bytes()).collect()
 }
 
 /// Converts a slice of words to a slice of bytes in little endian.
 pub fn words_to_bytes_le<const B: usize>(words: &[u32]) -> [u8; B] {
-    debug_assert_eq!(words.len() * 4, B);
-    words
-        .iter()
-        .flat_map(|word| word.to_le_bytes().to_vec())
-        .collect::<Vec<_>>()
-        .try_into()
-        .unwrap()
+    debug_assert_eq!(words.len() * WORD_SIZE, B);
+    let mut bytes = [0u8; B];
+    words.iter().enumerate().for_each(|(i, &word)| {
+        bytes[i * WORD_SIZE..(i + 1) * WORD_SIZE].copy_from_slice(&word.to_le_bytes());
+    });
+    bytes
 }
 
 /// Converts a byte array in little endian to a slice of words.
 pub fn bytes_to_words_le<const W: usize>(bytes: &[u8]) -> [u32; W] {
-    debug_assert_eq!(bytes.len(), W * 4);
-    bytes
-        .chunks_exact(4)
-        .map(|chunk| u32::from_le_bytes(chunk.try_into().unwrap()))
-        .collect::<Vec<_>>()
-        .try_into()
-        .unwrap()
+    debug_assert_eq!(bytes.len(), W * WORD_SIZE);
+    let mut words = [0u32; W];
+    bytes.chunks_exact(WORD_SIZE).enumerate().for_each(|(i, chunk)| {
+        words[i] = u32::from_le_bytes(chunk.try_into().unwrap());
+    });
+    words
 }
 
 /// Converts a byte array in little endian to a vector of words.
 pub fn bytes_to_words_le_vec(bytes: &[u8]) -> Vec<u32> {
     bytes
-        .chunks_exact(4)
+        .chunks_exact(WORD_SIZE)
         .map(|chunk| u32::from_le_bytes(chunk.try_into().unwrap()))
-        .collect::<Vec<_>>()
+        .collect()
 }
 
 // Converts a num to a string with commas every 3 digits.
@@ -54,3 +52,47 @@ pub fn num_to_comma_separated<T: ToString>(value: T) -> String {
         .rev()
         .collect()
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_words_to_bytes_le_vec() {
+        let words = [0x12345678, 0x90ABCDEF];
+        let expected = vec![0x78, 0x56, 0x34, 0x12, 0xEF, 0xCD, 0xAB, 0x90];
+        assert_eq!(words_to_bytes_le_vec(&words), expected);
+    }
+
+    #[test]
+    fn test_words_to_bytes_le() {
+        let words = [0x12345678, 0x90ABCDEF];
+        let expected: [u8; 8] = [0x78, 0x56, 0x34, 0x12, 0xEF, 0xCD, 0xAB, 0x90];
+        assert_eq!(words_to_bytes_le::<8>(&words), expected);
+    }
+
+    #[test]
+    fn test_bytes_to_words_le() {
+        let bytes = [0x78, 0x56, 0x34, 0x12, 0xEF, 0xCD, 0xAB, 0x90];
+        let expected = [0x12345678, 0x90ABCDEF];
+        assert_eq!(bytes_to_words_le::<2>(&bytes), expected);
+    }
+
+    #[test]
+    fn test_bytes_to_words_le_vec() {
+        let bytes = [0x78, 0x56, 0x34, 0x12, 0xEF, 0xCD, 0xAB, 0x90];
+        let expected = vec![0x12345678, 0x90ABCDEF];
+        assert_eq!(bytes_to_words_le_vec(&bytes), expected);
+    }
+
+    #[test]
+    fn test_num_to_comma_separated() {
+        assert_eq!(num_to_comma_separated(1000), "1,000");
+        assert_eq!(num_to_comma_separated(1000000), "1,000,000");
+        assert_eq!(num_to_comma_separated(987654321), "987,654,321");
+
+        // Test with a large number as BigUint
+        let large_num = num_bigint::BigUint::from(12345678901234567890u64);
+        assert_eq!(num_to_comma_separated(large_num), "12,345,678,901,234,567,890");
+    }
+}
diff --git a/crates/primitives/src/io.rs b/crates/primitives/src/io.rs
index 0d4d89e957..afc7cfb722 100644
--- a/crates/primitives/src/io.rs
+++ b/crates/primitives/src/io.rs
@@ -10,11 +10,6 @@ pub struct SP1PublicValues {
 }
 
 impl SP1PublicValues {
-    /// Create a new `SP1PublicValues`.
-    pub const fn new() -> Self {
-        Self { buffer: Buffer::new() }
-    }
-
     pub fn raw(&self) -> String {
         format!("0x{}", hex::encode(self.buffer.data.clone()))
     }
@@ -32,7 +27,7 @@ impl SP1PublicValues {
         self.buffer.data.clone()
     }
 
-    /// Read a value from the buffer.    
+    /// Read a value from the buffer.
     pub fn read<T: Serialize + DeserializeOwned>(&mut self) -> T {
         self.buffer.read()
     }
@@ -89,13 +84,84 @@ impl AsRef<[u8]> for SP1PublicValues {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use serde::{Deserialize, Serialize};
+
+    #[derive(Debug, Serialize, Deserialize, PartialEq)]
+    struct TestStruct {
+        a: u32,
+        b: String,
+    }
+
+    #[test]
+    fn test_new() {
+        let public_values = SP1PublicValues::default();
+        assert!(public_values.buffer.data.is_empty());
+    }
+
+    #[test]
+    fn test_from_slice() {
+        let data = b"test data";
+        let public_values = SP1PublicValues::from(data.as_ref());
+        assert_eq!(public_values.buffer.data, data);
+    }
+
+    #[test]
+    fn test_raw() {
+        let data = b"test raw data";
+        let public_values = SP1PublicValues::from(data.as_ref());
+        let expected_hex = format!("0x{}", hex::encode(data));
+        assert_eq!(public_values.raw(), expected_hex);
+    }
+
+    #[test]
+    fn test_as_slice() {
+        let data = b"test slice data";
+        let public_values = SP1PublicValues::from(data.as_ref());
+        assert_eq!(public_values.as_slice(), data);
+    }
+
+    #[test]
+    fn test_to_vec() {
+        let data = b"test vec data";
+        let public_values = SP1PublicValues::from(data.as_ref());
+        assert_eq!(public_values.to_vec(), data.to_vec());
+    }
+
+    #[test]
+    fn test_write_and_read() {
+        let mut public_values = SP1PublicValues::default();
+        let obj = TestStruct { a: 123, b: "test".to_string() };
+
+        public_values.write(&obj);
+        let read_obj: TestStruct = public_values.read();
+        assert_eq!(read_obj, obj);
+    }
+
+    #[test]
+    fn test_write_slice_and_read_slice() {
+        let mut public_values = SP1PublicValues::default();
+        let slice = [1, 2, 3, 4, 5];
+        public_values.write_slice(&slice);
+
+        let mut read_slice = [0; 5];
+        public_values.read_slice(&mut read_slice);
+        assert_eq!(read_slice, slice);
+    }
+
+    #[test]
+    fn test_hash() {
+        let data = b"some data to hash";
+        let public_values = SP1PublicValues::from(data.as_ref());
+        let expected_hash = Sha256::digest(data).to_vec();
+        assert_eq!(public_values.hash(), expected_hash);
+    }
 
     #[test]
     fn test_hash_public_values() {
         let test_hex = "1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef";
         let test_bytes = hex::decode(test_hex).unwrap();
 
-        let mut public_values = SP1PublicValues::new();
+        let mut public_values = SP1PublicValues::default();
         public_values.write_slice(&test_bytes);
         let hash = public_values.hash_bn254();
 
diff --git a/crates/primitives/src/types.rs b/crates/primitives/src/types.rs
index 6e0e2d326d..62dc49b59b 100644
--- a/crates/primitives/src/types.rs
+++ b/crates/primitives/src/types.rs
@@ -9,7 +9,7 @@ pub enum RecursionProgramType {
     Wrap,
 }
 
-/// A buffer of serializable/deserializable objects.                                              
+/// A buffer of serializable/deserializable objects.
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct Buffer {
     pub data: Vec<u8>,
@@ -26,12 +26,12 @@ impl Buffer {
         Self { data: data.to_vec(), ptr: 0 }
     }
 
-    /// Set the position ptr to the beginning of the buffer.                                      
+    /// Set the position ptr to the beginning of the buffer.
     pub fn head(&mut self) {
         self.ptr = 0;
     }
 
-    /// Read the serializable object from the buffer.                                             
+    /// Read the serializable object from the buffer.
     pub fn read<T: Serialize + DeserializeOwned>(&mut self) -> T {
         let result: T =
             bincode::deserialize(&self.data[self.ptr..]).expect("failed to deserialize");
@@ -45,14 +45,12 @@ impl Buffer {
         self.ptr += slice.len();
     }
 
-    /// Write the serializable object from the buffer.                                            
+    /// Write the serializable object from the buffer.
     pub fn write<T: Serialize>(&mut self, data: &T) {
-        let mut tmp = Vec::new();
-        bincode::serialize_into(&mut tmp, data).expect("serialization failed");
-        self.data.extend(tmp);
+        bincode::serialize_into(&mut self.data, data).expect("serialization failed");
     }
 
-    /// Write the slice of bytes to the buffer.                                                   
+    /// Write the slice of bytes to the buffer.
     pub fn write_slice(&mut self, slice: &[u8]) {
         self.data.extend_from_slice(slice);
     }
@@ -63,3 +61,109 @@ impl Default for Buffer {
         Self::new()
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use serde::{Deserialize, Serialize};
+
+    #[derive(Debug, Serialize, Deserialize, PartialEq)]
+    struct TestStruct {
+        a: u32,
+        b: String,
+    }
+
+    #[test]
+    fn test_new() {
+        let buffer = Buffer::new();
+        assert!(buffer.data.is_empty());
+        assert_eq!(buffer.ptr, 0);
+    }
+
+    #[test]
+    fn test_from_slice() {
+        let data: &[u8] = &[1, 2, 3, 4];
+        let buffer = Buffer::from(data);
+        assert_eq!(buffer.data, data);
+        assert_eq!(buffer.ptr, 0);
+    }
+
+    #[test]
+    fn test_head() {
+        let data: &[u8] = &[1, 2, 3, 4];
+        let mut buffer = Buffer::from(data);
+        buffer.ptr = 2;
+        buffer.head();
+        assert_eq!(buffer.ptr, 0);
+    }
+
+    #[test]
+    fn test_write_and_read() {
+        let mut buffer = Buffer::new();
+        let obj = TestStruct { a: 123, b: "test".to_string() };
+
+        // Serialize `obj` using bincode for comparison
+        let mut expected_data = Vec::new();
+        bincode::serialize_into(&mut expected_data, &obj).expect("serialization failed");
+
+        // Write `obj` to buffer and check if `buffer.data` matches `expected_data`
+        buffer.write(&obj);
+        assert_eq!(buffer.data, expected_data);
+        assert_eq!(buffer.ptr, 0);
+
+        let read_obj: TestStruct = buffer.read();
+        assert_eq!(read_obj, obj);
+        assert_eq!(buffer.ptr, buffer.data.len());
+    }
+
+    #[test]
+    fn test_write_slice_and_read_slice() {
+        let mut buffer = Buffer::new();
+        let slice = [1, 2, 3, 4, 5];
+
+        buffer.write_slice(&slice);
+        assert_eq!(buffer.data, slice);
+
+        let mut read_slice = [0; 5];
+        buffer.head();
+        buffer.read_slice(&mut read_slice);
+        assert_eq!(read_slice, slice);
+    }
+
+    #[test]
+    fn test_multiple_writes_and_reads() {
+        let mut buffer = Buffer::new();
+        let obj1 = TestStruct { a: 123, b: "first".to_string() };
+        let obj2 = TestStruct { a: 456, b: "second".to_string() };
+
+        buffer.write(&obj1);
+        buffer.write(&obj2);
+
+        buffer.head();
+        let read_obj1: TestStruct = buffer.read();
+        let read_obj2: TestStruct = buffer.read();
+
+        assert_eq!(read_obj1, obj1);
+        assert_eq!(read_obj2, obj2);
+    }
+
+    #[test]
+    fn test_default() {
+        let buffer: Buffer = Default::default();
+        assert!(buffer.data.is_empty());
+        assert_eq!(buffer.ptr, 0);
+    }
+
+    #[test]
+    fn test_pointer_after_read() {
+        let mut buffer = Buffer::new();
+        let obj = TestStruct { a: 789, b: "pointer_test".to_string() };
+
+        buffer.write(&obj);
+        buffer.head();
+        let start_ptr = buffer.ptr;
+
+        let _read_obj: TestStruct = buffer.read();
+        assert!(buffer.ptr > start_ptr, "Pointer should have advanced after read");
+    }
+}