Add a (failing) test for slicing at the same height of a horizontal surface attached to a volume. In this case, the loop isn't completed. #1672

utils/dump-stl.pl

@@ -18,6 +18,7 @@ $ARGV[0] or usage(1);
 
 if (-e $ARGV[0]) {
     my $model = Slic3r::Format::STL->read_file($ARGV[0]);
+    $model->objects->[0]->add_instance(offset => [0,0]);
     my $mesh = $model->mesh;
     $mesh->repair;
     printf "VERTICES = %s\n", join ',', map "[$_->[0],$_->[1],$_->[2]]", @{$mesh->vertices};