mononoke: add a test for MPathElement size

Summary: Add a test to detect any unexpected changes in MPatheElements size

Reviewed By: farnz

Differential Revision: D23703345

fbshipit-source-id: 74354f0861b048ee4611304fc99f0289bce4a7a5

eden/mononoke/mononoke_types/src/path.rs

@@ -1126,6 +1126,14 @@ where
 mod test {
     use super::*;
     use quickcheck::{quickcheck, TestResult};
+    use std::mem::size_of;
+
+    #[test]
+    fn test_mpath_element_size() {
+        // MPathElement size is important as we have a lot of them.
+        // Test so we are aware of any change.
+        assert_eq!(32, size_of::<MPathElement>());
+    }
 
     #[test]
     fn get_path_hash_multiple_elem() {