diff --git a/src/validate.rs b/src/validate.rs
index a9d3192..9cb7356 100644
--- a/src/validate.rs
+++ b/src/validate.rs
@@ -12,21 +12,10 @@ pub fn validate(verbosity: u8, config: util::config::Config) {
     let out_files: Vec<PathBuf> = get_dir_files(config.output_path).expect("Failed to read the output directory contents");
 
     let mismatch: Vec<(PathBuf, PathBuf)>;
-    let mut invalid_suffix_in: Vec<PathBuf> = vec![];
-    let mut invalid_suffix_out: Vec<PathBuf> = vec![];
 
-    // check if they end in .in or .out respectively
-    for file in in_files {
-        if !file.ends_with(in_suffix) {
-            invalid_suffix_in.push(file);
-        }
-    }
-
-    for file in out_files {
-        if !file.ends_with(out_suffix) {
-            invalid_suffix_out.push(file);
-        }
-    }
+    // check the files for valid suffixes
+    let invalid_suffix_in: Vec<PathBuf> = collect_invalid(&in_files, in_suffix);
+    let invalid_suffix_out: Vec<PathBuf> = collect_invalid(&out_files, out_suffix);
 
     // print the delinquints
     if invalid_suffix_in.len() > 0 {
@@ -40,6 +29,19 @@ pub fn validate(verbosity: u8, config: util::config::Config) {
     // make sure each has a match
 }
 
+fn collect_invalid(files: &Vec<PathBuf>, suf: &str) -> Vec<PathBuf> {
+    let mut res: Vec<PathBuf> = vec![];
+
+    for file in files {
+        let extension = file.extension().expect("Invalid file name for validation");
+        if extension.to_str() != Some(suf) {
+            res.push(file.clone());
+        }
+    }
+
+    return res
+}
+
 fn get_dir_files(path: PathBuf) -> Result<Vec<PathBuf>, &'static str>  {
     let mut res: Vec<PathBuf> = vec![];
 
@@ -64,14 +66,14 @@ fn get_dir_files(path: PathBuf) -> Result<Vec<PathBuf>, &'static str>  {
 fn compare_files(in_files: Vec<PathBuf>, out_files: Vec<PathBuf>) -> Vec<PathBuf> {
     let mut res: Vec<PathBuf> = vec![];
 
-    res.append(&mut compare_list(in_files, out_files));
-    res.append(&mut compare_list(out_files, in_files));
+    res.append(&mut compare_list(&in_files, &out_files));
+    res.append(&mut compare_list(&out_files, &in_files));
 
     return res;
 }
 
-fn compare_list(from: Vec<PathBuf>, against: Vec<PathBuf>) -> Vec<PathBuf> {
-    let res: Vec<PathBuf> = vec![];
+fn compare_list(from: &Vec<PathBuf>, against: &Vec<PathBuf>) -> Vec<PathBuf> {
+    let mut res: Vec<PathBuf> = vec![];
 
     // Compare each input file to each output file
     for file in from {
@@ -81,7 +83,7 @@ fn compare_list(from: Vec<PathBuf>, against: Vec<PathBuf>) -> Vec<PathBuf> {
                 break;
             }
         }
-        res.push(file); // if the file does not have a counterpart, then push to the lost files
+        res.push(file.clone()); // if the file does not have a counterpart, then push to the lost files
     }
 
     return res;
@@ -96,11 +98,37 @@ fn print_invalid_suffixes(files: Vec<PathBuf>, exp: String) {
             _       => panic!("Failed to load the file"),
         };
 
-        println!("{} => {}", initial, file.set_extension(exp).to_string());
+        println!("{} => {}", initial, file.clone().set_extension(&exp).to_string());
     }
 }
 
 #[cfg(test)]
 mod tests {
+    use super::*;
 
+    #[test]
+    fn test_collect_invalid() {
+        let suffix = "suf";
+        let valid_path1 = PathBuf::from("path/file.suf");
+        let valid_path2 = PathBuf::from("path/file_stupid.suf");
+        let valid_path3 = PathBuf::from("path/file/dead.suf");
+        let invalid_path1 = PathBuf::from("path/file.sub");
+        let invalid_path2 = PathBuf::from("path/file_stupid.sur");
+        let invalid_path3 = PathBuf::from("path/file.bub");
+
+        let files: Vec<PathBuf> = vec![valid_path1.clone(), valid_path2.clone(), valid_path3.clone(),
+                                       invalid_path1.clone(), invalid_path2.clone(), invalid_path3.clone()];
+
+        let invalid = collect_invalid(&files, suffix);
+
+        println!("{:?}", invalid);
+
+        assert!(invalid.contains(&invalid_path1));
+        assert!(invalid.contains(&invalid_path2));
+        assert!(invalid.contains(&invalid_path3));
+
+        assert!(!invalid.contains(&valid_path1));
+        assert!(!invalid.contains(&valid_path2));
+        assert!(!invalid.contains(&valid_path3));
+    }
 }