Tests for the flattened in bigint case.

t/nqp/60-bigint.t

@@ -1,5 +1,7 @@
 #! nqp
-plan(16);
+use nqpmo;
+
+plan(19);
 
 pir::nqp_bigint_setup__v();
 
@@ -34,3 +36,18 @@ ok(iseq(nqp::bitor_I( box(0xdead), box(0xbeef)), 0xfeef), 'bit or');
 ok(iseq(nqp::bitxor_I(box(0xdead), box(0xbeef)), 0x6042), 'bit xor');
 
 ok(iseq(nqp::bitneg_I(box(-123)), 122), 'bit negation');
+
+
+# Now we'll create a type that boxes a P6bigint.
+my $bi_boxer := $knowhow.new_type(:name('TestPerl6Int'), :repr('P6opaque'));
+$bi_boxer.HOW.add_attribute($bi_boxer, NQPAttribute.new(
+    :name('$!value'), :type($bi_type), :box_target(1)
+));
+$bi_boxer.HOW.compose($bi_boxer);
+
+# Try some basic operations with it.
+my $box_val_1 := nqp::box_i(4, $bi_boxer);
+ok(iseq($box_val_1, 4), 'can box to a complex type with a P6bigint target');
+my $box_val_2 := pir::nqp_bigint_from_str__PPS($bi_boxer, '38');
+ok(iseq($box_val_2, 38), 'can get a bigint from a string with boxing type');
+ok(iseq(nqp::add_I($box_val_1, $box_val_2), 42), 'addition works on boxing type');