Feat: Add small test case for practice.

src/main.rs

@@ -28,3 +28,13 @@ fn main() -> Result<()> {
 
     Ok(())
 }
+
+#[allow(dead_code)]
+fn answer() -> i32 {
+    return 42;
+}
+
+#[test]
+fn check_answer_validity() {
+    assert_eq!(answer(), 42);
+}