add test

Author: marcoieni

src/main.rs

@@ -1,3 +1,17 @@
 fn main() {
-    println!("Hello, world!!");
+    println!("Hello, world!");
+}
+
+fn answer() -> u32 {
+    42
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn deep_thought_test() {
+        assert_eq!(answer(), 42);
+    }
 }