feat: Add traits3.rs exercise

exercises/traits/traits3.rs

@@ -0,0 +1,40 @@
+// traits3.rs
+//
+// Your task is to implement the Licensed trait for
+// both structures and have them return the same
+// information without writing the same function twice.
+//
+// Consider what you can add to the Licensed trait.
+
+// I AM NOT DONE
+
+pub trait Licensed {
+    fn licensing_info(&self) -> String;
+}
+
+struct SomeSoftware {
+    version_number: i32,
+}
+
+struct OtherSoftware {
+    version_number: String,
+}
+
+impl Licensed for SomeSoftware {} // Don't edit this line
+impl Licensed for OtherSoftware {} // Don't edit this line
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn is_licensing_info_the_same() {
+        let licensing_info = String::from("Some information");
+        let some_software = SomeSoftware { version_number: 1 };
+        let other_software = OtherSoftware {
+            version_number: "v2.0.0".to_string(),
+        };
+        assert_eq!(some_software.licensing_info(), licensing_info);
+        assert_eq!(other_software.licensing_info(), licensing_info);
+    }
+}