Add tests

src/main.rs

@@ -86,3 +86,63 @@ struct Song {
     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")]))
+    }
+}