diff --git a/tests/cryptopals.rs b/tests/cryptopals.rs
index 9960cfc..ca84879 100644
--- a/tests/cryptopals.rs
+++ b/tests/cryptopals.rs
@@ -4,11 +4,14 @@
 extern crate cryptopals;
 
 use std::f32;
+use std::fs::File;
+use std::io::{BufRead, BufReader};
 use cryptopals::b64::Base64Encodable;
 use cryptopals::hex::{HexDecodable, HexEncodable};
 use cryptopals::letter_frequency::LetterFreq;
 use cryptopals::xor::{FixedXOR, ByteXOR};
 
+/// Base 64 encode some bytes.
 #[test]
 fn s1c1() {
     let input = "49276d206b696c6c696e6720796f757220627261696e206c696b65206120706f69736f6e6f7573206d757368726f6f6d";
@@ -17,6 +20,7 @@ fn s1c1() {
     assert_eq!(output, ex_output);
 }
 
+/// XOR two arrays of bytes together to get a new byte string.
 #[test]
 fn s1c2() {
     let a = "1c0111001f010100061a024b53535009181c";
@@ -28,6 +32,7 @@ fn s1c2() {
     assert_eq!(output, ex_output);
 }
 
+/// Determine the key for a single byte XOR encryption scheme using English letter frequency analysis.
 #[test]
 fn s1c3() {
     let input = "1b37373331363f78151b7f2b783431333d78397828372d363c78373e783a393b3736";
@@ -51,3 +56,18 @@ fn s1c3() {
     println!("{}: {:?} -> {}", best_key, best_output, best_score);
     assert!(best_output.to_lowercase().contains("bacon"));
 }
+
+/// Detect a single byte XOR encryption scheme using the letter frequency analysis from s1c3.
+#[test]
+fn s1c4() {
+    let f = match File::open("resources/s1c4.txt") {
+        Ok(f) => f,
+        Err(e) => panic!("failed to open the strings file: {}", e),
+    };
+    let reader = BufReader::new(&f);
+    for line in reader.lines() {
+        let line = line.unwrap();
+        println!("{:?}", line);
+        let bytes = line.chars().hex_decoded();
+    }
+}