I'm not sure if you saying that the DelegateObject still having a strong reference is a bug in the test code or not. If you're setting the session delegate to nil (and remove all the code waiting for the didBecomeInvalidExp to be fullfilled), then you'll see the test passes.

It seems that the problem in my case comes from when the svg has a filter tag with a width or height > 100% and unit "objectBoundingBox". (the filter was a gaussianblur)

actually the gaussianblur filter crash, no need for a width or height > 100%