-is($assembly->type, 'assembly', 'assembly has correct type');
-is( scalar @{$assembly->assemblies}, 2, 'assembly consists of two parts' );
+is($assembly_part->inventory_accno_id, undef, "assembly doesn't have an inventory accno id");
+
+is($assembly_part->type, 'assembly', 'assembly has correct type');
+is( scalar @{$assembly_part->assemblies}, 2, 'assembly consists of two parts' );
+
+# fetch assembly item corresponding to partnumber 19000
+my $assembly_items = $assembly_part->find_assemblies( { parts_id => $assembly_item_part->id } ) || die "can't find assembly_item";
+my $assembly_item = $assembly_items->[0];
+is($assembly_item->part->partnumber, '19000', 'assembly part part relation works');
+is($assembly_item->assembly_part->partnumber, 'as1', 'assembly part assembly part relation works');