diff --git a/set1/challenge1_hex2base64/src/main.rs b/set1/challenge1_hex2base64/src/main.rs
index a6e182e..25f104b 100644
--- a/set1/challenge1_hex2base64/src/main.rs
+++ b/set1/challenge1_hex2base64/src/main.rs
@@ -5,12 +5,23 @@ use std::io::{BufRead, stdin};
 
 fn main() {
     env_logger::init();
-    let stdin = stdin();
 
-    for line in stdin.lock().lines().filter_map(|x| x.ok()) {
+    for line in stdin().lock().lines().filter_map(|x| x.ok()) {
         match line.from_hex() {
             Ok(v) => println!("{}", v.to_base64(STANDARD)),
             Err(e) => error!("{}", e)
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn challenge1_hex2base64() {
+        let v = "49276d206b696c6c696e6720796f757220627261696e206c696b65206120706f69736f6e6f7573206d757368726f6f6d".from_hex().unwrap();
+        let r = v.to_base64(STANDARD);
+        assert_eq!(r, "SSdtIGtpbGxpbmcgeW91ciBicmFpbiBsaWtlIGEgcG9pc29ub3VzIG11c2hyb29t");
+    }
+}
diff --git a/set1/challenge2_fixed_xor/src/main.rs b/set1/challenge2_fixed_xor/src/main.rs
index 6fcf1cf..8f79338 100644
--- a/set1/challenge2_fixed_xor/src/main.rs
+++ b/set1/challenge2_fixed_xor/src/main.rs
@@ -19,9 +19,8 @@ impl<T> Iterator for Pairwise<T> where T: Iterator {
 
 fn main() {
     env_logger::init();
-    let stdin = stdin();
 
-    for (line1, line2) in Pairwise(stdin.lock().lines().filter_map(|x| x.ok())) {
+    for (line1, line2) in Pairwise(stdin().lock().lines().filter_map(|x| x.ok())) {
         match (line1.from_hex(), line2.from_hex()) {
             (Ok(v1), Ok(v2)) => println!("{}", fixed_xor_cipher(&v1, &mut v2.into_iter()).to_hex()),
             (Err(e), _) => error!("{}", e),
@@ -29,3 +28,16 @@ fn main() {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn challenge2_fixed_xor() {
+        let v1 = "1c0111001f010100061a024b53535009181c".from_hex().unwrap();
+        let v2 = "686974207468652062756c6c277320657965".from_hex().unwrap();
+        let r = fixed_xor_cipher(&v1, &mut v2.into_iter()).to_hex();
+        assert_eq!(r, "746865206b696420646f6e277420706c6179");
+    }
+}
diff --git a/set1/challenge3_xor_cipher/src/main.rs b/set1/challenge3_xor_cipher/src/main.rs
index 854696a..5caff28 100644
--- a/set1/challenge3_xor_cipher/src/main.rs
+++ b/set1/challenge3_xor_cipher/src/main.rs
@@ -5,9 +5,8 @@ use std::io::{BufRead, stdin};
 
 fn main() {
     env_logger::init();
-    let stdin = stdin();
 
-    for line in stdin.lock().lines().filter_map(|x| x.ok()) {
+    for line in stdin().lock().lines().filter_map(|x| x.ok()) {
         match line.from_hex() {
             Ok(ciphertext) => {
                 let (decrypted, _) = break_xor_cipher(&ciphertext);
@@ -20,3 +19,15 @@ fn main() {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn challenge3_xor_cipher() {
+        let ciphertext = "1b37373331363f78151b7f2b783431333d78397828372d363c78373e783a393b3736".from_hex().unwrap();
+        let (decrypted, _) = break_xor_cipher(&ciphertext);
+        assert_eq!(String::from_utf8(decrypted).unwrap(), "Cooking MC's like a pound of bacon");
+    }
+}
diff --git a/set1/challenge4_detect_xor/src/main.rs b/set1/challenge4_detect_xor/src/main.rs
index 1b33b7d..e931c4b 100644
--- a/set1/challenge4_detect_xor/src/main.rs
+++ b/set1/challenge4_detect_xor/src/main.rs
@@ -1,28 +1,44 @@
 use common::break_xor_cipher;
 use log::error;
 use rustc_serialize::hex::FromHex;
+use std::error::Error;
 use std::io::{BufRead, stdin};
 
-fn main() {
-    env_logger::init();
-    let stdin = stdin();
+fn detect_xor(input: &mut dyn BufRead) -> Result<String, Box<dyn Error>> {
     let mut maxscore = 0;
     let mut decrypted: Vec<u8> = vec![];
 
-    for line in stdin.lock().lines().filter_map(|x| x.ok()) {
-        match line.from_hex() {
-            Ok(ciphertext) => {
-                let (plaintext, score) = break_xor_cipher(&ciphertext);
-                if score > maxscore {
-                    maxscore = score;
-                    decrypted = plaintext;
-                }
-            }
-            Err(e) => error!("{}", e)
+    for line in input.lines() {
+        let ciphertext = line?.from_hex()?;
+        let (plaintext, score) = break_xor_cipher(&ciphertext);
+        if score > maxscore {
+            maxscore = score;
+            decrypted = plaintext;
         }
     }
-    match String::from_utf8(decrypted) {
+    Ok(String::from_utf8(decrypted)?)
+}
+
+fn main() {
+    env_logger::init();
+
+    match detect_xor(&mut stdin().lock()) {
         Ok(s) => println!("{}", s),
         Err(e) => error!("{}", e)
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use std::fs::File;
+    use std::io::BufReader;
+    use std::path::Path;
+    use super::*;
+
+    #[test]
+    fn challenge4_detect_xor() {
+        let cargo_manifest_dir = Path::new(env!("CARGO_MANIFEST_DIR"));
+        let testinput = File::open(cargo_manifest_dir.join("4.txt")).unwrap();
+        assert_eq!(detect_xor(&mut BufReader::new(testinput)).unwrap(), "Now that the party is jumping\n");
+    }
+}