Add derive related tests

Author: DJMcNab

tests/test_derive_input.rs

@@ -1,3 +1,7 @@
+// These tests are also duplicated in "test_derive_input_with_default", but for the "default field values" version of the derive input
+// If editing these tests, if there is an equivalent test in the other file, you should edit that too.
+// If adding a new test, you should also add it to the other file.
+
 #![allow(
     clippy::assertions_on_result_states,
     clippy::elidable_lifetime_names,