Clean up and unify exercises

exercises/06_move_semantics/move_semantics5.rs

@@ -1,17 +1,21 @@
-// move_semantics5.rs
-//
-// Make me compile only by reordering the lines in `main()`, but without adding,
+// Make me compile only by reordering the lines in the test, but without adding,
 // changing or removing any of them.
-//
-// Execute `rustlings hint move_semantics5` or use the `hint` watch subcommand
-// for a hint.
 
-#[test]
 fn main() {
-    let mut x = 100;
-    let y = &mut x;
-    let z = &mut x;
-    *y += 100;
-    *z += 1000;
-    assert_eq!(x, 1200);
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn move_semantics5() {
+        let mut x = 100;
+        let y = &mut x;
+        let z = &mut x;
+        *y += 100;
+        *z += 1000;
+        assert_eq!(x, 1200);
+    }
 }