Of course you should income-test GIS.
For OAS we have an income test now; the clawback starts at around $75,000. We could talk about how you might want to play with it.
For CPP there is no income testing.
I will make the comment that we spend about $10 billion to $11 billion a year on GIS. We spend $35 billion to $40 billion a year on OAS. We spend about $60 billion a year on tax assistance for RRSPs and pensions. For every dollar we spend on low-income seniors, we spend something like $7 on high-income seniors.