Add integrity test for slash defer duration

frame/staking/src/lib.rs

@@ -1459,6 +1459,13 @@ decl_module! {
 			// `on_finalize` weight is tracked in `on_initialize`
 		}
 
+		fn integrity_test() {
+			assert!(
+				T::SlashDeferDuration::get() < T::BondingDuration::get() || T::BondingDuration::get() == 0,
+				"As per documentation, slash defer duration should be less than bonding duration.",
+			);
+		}
+
 		/// Take the origin account as a stash and lock up `value` of its balance. `controller` will
 		/// be the account that controls it.
 		///