diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..9885774
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,23 @@
+pub struct Person {
+    pub age: i32,
+    pub name: String,
+}
+
+impl ToString for Person {
+    /// # Examples
+    ///
+    /// ```
+    /// use rust_tutorial::Person;
+    ///
+    /// let p = Person { age: 30, name: "Mary".to_string() };
+    /// assert_eq!(p.to_string(), "Mary (30)");
+    /// ```
+    fn to_string(&self) -> String {
+        format!("{} ({})", self.name, self.age)
+    }
+}
+
+#[test]
+fn test_example() {
+    assert_eq!("a", "a");
+}