diff --git a/src/library.rs b/src/library.rs
new file mode 100644
index 0000000..d4db4ab
--- /dev/null
+++ b/src/library.rs
@@ -0,0 +1,128 @@
+use nanoserde::DeJson;
+use std::{
+    collections::{HashMap, HashSet},
+    hash::Hash,
+};
+
+#[derive(Debug, Clone)]
+pub struct Library {
+    artists: HashSet<Artist>,
+}
+
+impl Library {
+    pub fn new(json: HashMap<String, Vec<Song>>) -> Self {
+        let artists = json
+            .into_iter()
+            .map(|(name, catalog)| Artist {
+                name,
+                catalog: catalog.into_iter().collect(),
+            })
+            .collect();
+        Library { artists }
+    }
+
+    pub fn find_covers(&self) -> HashSet<&Song> {
+        let names = self
+            .artists
+            .iter()
+            .map(|artist| artist.name.clone())
+            .collect::<HashSet<_>>();
+        self.artists
+            .iter()
+            .fold(HashSet::new(), |mut covers, artist| {
+                covers.extend(artist.covered_songs());
+                covers
+            })
+            .into_iter()
+            .filter(|song| names.contains(&song.composer))
+            .collect()
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+struct Artist {
+    name: String,
+    catalog: HashSet<Song>,
+}
+
+impl Hash for Artist {
+    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
+        self.name.hash(state);
+    }
+}
+
+impl Artist {
+    fn covered_songs(&self) -> HashSet<&Song> {
+        self.catalog
+            .iter()
+            .filter(|song| song.composer != self.name)
+            .collect()
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash, DeJson)]
+pub struct Song {
+    pub title: String,
+    pub performer: String,
+    pub composer: String,
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn bmbmbm() -> Song {
+        Song {
+            title: "bmbmbm".to_string(),
+            performer: "black midi".to_string(),
+            composer: "black midi".to_string(),
+        }
+    }
+
+    fn love_story(performer: &str) -> Song {
+        Song {
+            title: "Love Story".to_string(),
+            performer: performer.to_string(),
+            composer: "Taylor Swift".to_string(),
+        }
+    }
+
+    fn schizoid_man() -> Song {
+        Song {
+            title: "21st Century Schizoid Man".to_string(),
+            performer: "black midi".to_string(),
+            composer: "Greg Lake, Ian McDonald, Michael Giles, Peter Sinfield & Robert Fripp"
+                .to_string(),
+        }
+    }
+
+    fn bm() -> Artist {
+        Artist {
+            name: "black midi".to_string(),
+            catalog: HashSet::from([bmbmbm(), love_story("black midi"), schizoid_man()]),
+        }
+    }
+
+    fn ts() -> Artist {
+        Artist {
+            name: "Taylor Swift".to_string(),
+            catalog: HashSet::from([love_story("Taylor Swift")]),
+        }
+    }
+
+    fn library() -> Library {
+        Library {
+            artists: HashSet::from([bm(), ts()]),
+        }
+    }
+
+    #[test]
+    fn test_covered_songs() {
+        assert!(bm().covered_songs() == HashSet::from([&love_story("black midi"), &schizoid_man()]))
+    }
+
+    #[test]
+    fn test_find_covers() {
+        assert!(library().find_covers() == HashSet::from([&love_story("black midi")]))
+    }
+}
diff --git a/src/main.rs b/src/main.rs
index 12eb334..dcfa765 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,9 +1,8 @@
 use nanoserde::DeJson;
-use std::{
-    collections::{HashMap, HashSet},
-    env, fs,
-    hash::Hash,
-};
+use std::{collections::HashMap, env, fs};
+
+mod library;
+use crate::library::{Library, Song};
 
 fn main() {
     let file_path = env::args()
@@ -21,128 +20,3 @@ fn main() {
         )
     }
 }
-
-#[derive(Debug, Clone)]
-struct Library {
-    artists: HashSet<Artist>,
-}
-
-impl Library {
-    fn new(json: HashMap<String, Vec<Song>>) -> Self {
-        let artists = json
-            .into_iter()
-            .map(|(name, catalog)| Artist {
-                name,
-                catalog: catalog.into_iter().collect(),
-            })
-            .collect();
-        Library { artists }
-    }
-}
-
-impl Library {
-    fn find_covers(&self) -> HashSet<&Song> {
-        let names = self
-            .artists
-            .iter()
-            .map(|artist| artist.name.clone())
-            .collect::<HashSet<_>>();
-        self.artists
-            .iter()
-            .fold(HashSet::new(), |mut covers, artist| {
-                covers.extend(artist.covered_songs());
-                covers
-            })
-            .into_iter()
-            .filter(|song| names.contains(&song.composer))
-            .collect()
-    }
-}
-
-#[derive(Debug, Clone, PartialEq, Eq)]
-struct Artist {
-    name: String,
-    catalog: HashSet<Song>,
-}
-
-impl Hash for Artist {
-    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
-        self.name.hash(state);
-    }
-}
-
-impl Artist {
-    fn covered_songs(&self) -> HashSet<&Song> {
-        self.catalog
-            .iter()
-            .filter(|song| song.composer != self.name)
-            .collect()
-    }
-}
-
-#[derive(Debug, Clone, PartialEq, Eq, Hash, DeJson)]
-struct Song {
-    title: String,
-    performer: String,
-    composer: String,
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    fn bmbmbm() -> Song {
-        Song {
-            title: "bmbmbm".to_string(),
-            performer: "black midi".to_string(),
-            composer: "black midi".to_string(),
-        }
-    }
-
-    fn love_story(performer: &str) -> Song {
-        Song {
-            title: "Love Story".to_string(),
-            performer: performer.to_string(),
-            composer: "Taylor Swift".to_string(),
-        }
-    }
-
-    fn schizoid_man() -> Song {
-        Song {
-            title: "21st Century Schizoid Man".to_string(),
-            performer: "black midi".to_string(),
-            composer: "Greg Lake, Ian McDonald, Michael Giles, Peter Sinfield & Robert Fripp"
-                .to_string(),
-        }
-    }
-
-    fn bm() -> Artist {
-        Artist {
-            name: "black midi".to_string(),
-            catalog: HashSet::from([bmbmbm(), love_story("black midi"), schizoid_man()]),
-        }
-    }
-
-    fn ts() -> Artist {
-        Artist {
-            name: "Taylor Swift".to_string(),
-            catalog: HashSet::from([love_story("Taylor Swift")]),
-        }
-    }
-
-    fn library() -> Library {
-        Library {
-            artists: HashSet::from([bm(), ts()]),
-        }
-    }
-
-    #[test]
-    fn test_covered_songs() {
-        assert!(bm().covered_songs() == HashSet::from([&love_story("black midi"), &schizoid_man()]))
-    }
-
-    #[test]
-    fn test_find_covers() {
-        assert!(library().find_covers() == HashSet::from([&love_story("black midi")]))
-    }
-}