Add some Date subclassing tests

S32-temporal/Date.t

@@ -3,7 +3,7 @@ use Test;
 
 # L<S32::Temporal/C<Date>>
 
-plan 88;
+plan 100;
 
 # construction
 {
@@ -173,3 +173,14 @@ is Date.new('2015-12-29',:formatter({sprintf "%2d/%2d/%4d",.day,.month,.year})),
     class BarDate is Date does Foo {}
     is BarDate.today.a, [7,8,9], 'did role attributes get initialized ok';
 }
+
+{
+    class FooDate is Date { has $.foo };
+    for (2016,2,20), '2016-02-20', \(:2016year,:2month,:20day) -> $date {
+        my $fd = FooDate.new(|$date, foo => 42);
+        is $fd.year, 2016, "is year in FooDate ok";
+        is $fd.month,   2, "is month in FooDate ok";
+        is $fd.day,    20, "is day in FooDate ok";
+        is $fd.foo,    42, "is foo in FooDate ok";
+    }
+}