Improve core::option coverage

Author: pvdrz

library/coretests/tests/option.rs

@@ -248,6 +248,12 @@ fn test_unwrap_or_else() {
     */
 }
 
+#[test]
+fn test_unwrap_or_default() {
+    assert_eq!(Some(666u32).unwrap_or_default(), 666);
+    assert_eq!(None::<u32>.unwrap_or_default(), 0);
+}
+
 #[test]
 fn test_unwrap_unchecked() {
     assert_eq!(unsafe { Some(1).unwrap_unchecked() }, 1);